diff --git a/app/frontend/build.gradle.kts b/app/frontend/build.gradle.kts
index 7df9965..6441ae2 100644
--- a/app/frontend/build.gradle.kts
+++ b/app/frontend/build.gradle.kts
@@ -34,6 +34,23 @@ dependencies {
     implementation(platform("androidx.compose:compose-bom:2024.12.01"))
     implementation("androidx.compose.ui:ui")
     implementation("androidx.compose.material3:material3")
+    implementation("androidx.compose.material:material-icons-extended")
     implementation("androidx.activity:activity-compose:1.9.3")
     implementation("androidx.navigation:navigation-compose:2.8.5")
+
+    // Networking
+    implementation("com.squareup.retrofit2:retrofit:2.11.0")
+    implementation("com.squareup.retrofit2:converter-gson:2.11.0")
+    implementation("com.squareup.okhttp3:okhttp:4.12.0")
+
+    // Image Loading
+    implementation("io.coil-kt:coil-compose:2.7.0")
+
+    // Video Player
+    implementation("androidx.media3:media3-exoplayer:1.5.1")
+    implementation("androidx.media3:media3-ui:1.5.1")
+
+    // ViewModel
+    implementation("androidx.lifecycle:lifecycle-viewmodel-compose:2.8.7")
+    implementation("androidx.lifecycle:lifecycle-runtime-compose:2.8.7")
 }
diff --git a/app/frontend/src/main/AndroidManifest.xml b/app/frontend/src/main/AndroidManifest.xml
index 5e16b30..5218c6a 100644
--- a/app/frontend/src/main/AndroidManifest.xml
+++ b/app/frontend/src/main/AndroidManifest.xml
@@ -6,6 +6,7 @@
     <application
         android:allowBackup="true"
         android:label="YouTube App"
+        android:usesCleartextTraffic="true"
         android:theme="@android:style/Theme.Material.Light.NoActionBar">
 
         <activity
diff --git a/app/frontend/src/main/java/com/youtubeapp/MainActivity.kt b/app/frontend/src/main/java/com/youtubeapp/MainActivity.kt
index 2200c4c..e5174e7 100644
--- a/app/frontend/src/main/java/com/youtubeapp/MainActivity.kt
+++ b/app/frontend/src/main/java/com/youtubeapp/MainActivity.kt
@@ -3,13 +3,16 @@ package com.youtubeapp
 import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
-import androidx.compose.material3.Text
+import com.youtubeapp.ui.navigation.AppNavigation
+import com.youtubeapp.ui.theme.YouTubeAppTheme
 
 class MainActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContent {
-            Text("YouTube App")
+            YouTubeAppTheme {
+                AppNavigation()
+            }
         }
     }
 }
diff --git a/app/frontend/src/main/java/com/youtubeapp/data/ApiClient.kt b/app/frontend/src/main/java/com/youtubeapp/data/ApiClient.kt
new file mode 100644
index 0000000..65a051a
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/data/ApiClient.kt
@@ -0,0 +1,17 @@
+package com.youtubeapp.data
+
+import retrofit2.Retrofit
+import retrofit2.converter.gson.GsonConverterFactory
+
+object ApiClient {
+    // Server-IP hier anpassen
+    const val BASE_URL = "http://192.168.178.92:8000/"
+
+    val api: VideoApi by lazy {
+        Retrofit.Builder()
+            .baseUrl(BASE_URL)
+            .addConverterFactory(GsonConverterFactory.create())
+            .build()
+            .create(VideoApi::class.java)
+    }
+}
diff --git a/app/frontend/src/main/java/com/youtubeapp/data/Video.kt b/app/frontend/src/main/java/com/youtubeapp/data/Video.kt
new file mode 100644
index 0000000..d4c6d78
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/data/Video.kt
@@ -0,0 +1,11 @@
+package com.youtubeapp.data
+
+data class Video(
+    val id: Int,
+    val title: String,
+    val youtuber: String,
+    val thumbnail_url: String,
+    val youtube_url: String,
+    val is_downloaded: Boolean,
+    val created_at: String
+)
diff --git a/app/frontend/src/main/java/com/youtubeapp/data/VideoApi.kt b/app/frontend/src/main/java/com/youtubeapp/data/VideoApi.kt
new file mode 100644
index 0000000..2a5ae05
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/data/VideoApi.kt
@@ -0,0 +1,16 @@
+package com.youtubeapp.data
+
+import retrofit2.http.GET
+import retrofit2.http.POST
+import retrofit2.http.Path
+
+interface VideoApi {
+    @GET("videos")
+    suspend fun getAllVideos(): List<Video>
+
+    @GET("videos/downloaded")
+    suspend fun getDownloadedVideos(): List<Video>
+
+    @POST("videos/{id}/download")
+    suspend fun triggerDownload(@Path("id") id: Int): Map<String, String>
+}
diff --git a/app/frontend/src/main/java/com/youtubeapp/data/VideoRepository.kt b/app/frontend/src/main/java/com/youtubeapp/data/VideoRepository.kt
new file mode 100644
index 0000000..fca7244
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/data/VideoRepository.kt
@@ -0,0 +1,15 @@
+package com.youtubeapp.data
+
+class VideoRepository(private val api: VideoApi = ApiClient.api) {
+
+    suspend fun getAllVideos(): Result<List<Video>> = runCatching { api.getAllVideos() }
+
+    suspend fun getDownloadedVideos(): Result<List<Video>> = runCatching { api.getDownloadedVideos() }
+
+    suspend fun triggerDownload(videoId: Int): Result<String> = runCatching {
+        val response = api.triggerDownload(videoId)
+        response["status"] ?: "unknown"
+    }
+
+    fun getStreamUrl(videoId: Int): String = "${ApiClient.BASE_URL}videos/$videoId/stream"
+}
diff --git a/app/frontend/src/main/java/com/youtubeapp/ui/components/VideoCard.kt b/app/frontend/src/main/java/com/youtubeapp/ui/components/VideoCard.kt
new file mode 100644
index 0000000..a54c84e
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/ui/components/VideoCard.kt
@@ -0,0 +1,50 @@
+package com.youtubeapp.ui.components
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.aspectRatio
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.Card
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import coil.compose.AsyncImage
+import com.youtubeapp.data.Video
+
+@Composable
+fun VideoCard(video: Video, onClick: () -> Unit) {
+    Card(
+        onClick = onClick,
+        modifier = Modifier.fillMaxWidth()
+    ) {
+        Column {
+            AsyncImage(
+                model = video.thumbnail_url,
+                contentDescription = video.title,
+                contentScale = ContentScale.Crop,
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .aspectRatio(16f / 9f)
+            )
+            Column(modifier = Modifier.padding(8.dp)) {
+                Text(
+                    text = video.title,
+                    style = MaterialTheme.typography.titleSmall,
+                    maxLines = 2,
+                    overflow = TextOverflow.Ellipsis
+                )
+                Text(
+                    text = video.youtuber,
+                    style = MaterialTheme.typography.bodySmall,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    maxLines = 1,
+                    overflow = TextOverflow.Ellipsis
+                )
+            }
+        }
+    }
+}
diff --git a/app/frontend/src/main/java/com/youtubeapp/ui/navigation/AppNavigation.kt b/app/frontend/src/main/java/com/youtubeapp/ui/navigation/AppNavigation.kt
new file mode 100644
index 0000000..e9ab6e1
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/ui/navigation/AppNavigation.kt
@@ -0,0 +1,106 @@
+package com.youtubeapp.ui.navigation
+
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Download
+import androidx.compose.material.icons.filled.VideoLibrary
+import androidx.compose.material3.Icon
+import androidx.compose.material3.NavigationBar
+import androidx.compose.material3.NavigationBarItem
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Modifier
+import androidx.lifecycle.viewmodel.compose.viewModel
+import androidx.navigation.NavGraph.Companion.findStartDestination
+import androidx.navigation.NavType
+import androidx.navigation.compose.NavHost
+import androidx.navigation.compose.composable
+import androidx.navigation.compose.currentBackStackEntryAsState
+import androidx.navigation.compose.rememberNavController
+import androidx.navigation.navArgument
+import com.youtubeapp.ui.screens.AllVideosScreen
+import com.youtubeapp.ui.screens.DownloadedScreen
+import com.youtubeapp.ui.screens.VideoDetailScreen
+import com.youtubeapp.ui.screens.VideoPlayerScreen
+import com.youtubeapp.ui.viewmodel.VideoViewModel
+
+@Composable
+fun AppNavigation() {
+    val navController = rememberNavController()
+    val viewModel: VideoViewModel = viewModel()
+    val navBackStackEntry by navController.currentBackStackEntryAsState()
+    val currentRoute = navBackStackEntry?.destination?.route
+
+    val showBottomBar = currentRoute in listOf(Route.AllVideos.route, Route.Downloaded.route)
+
+    Scaffold(
+        bottomBar = {
+            if (showBottomBar) {
+                NavigationBar {
+                    NavigationBarItem(
+                        selected = currentRoute == Route.AllVideos.route,
+                        onClick = {
+                            navController.navigate(Route.AllVideos.route) {
+                                popUpTo(navController.graph.findStartDestination().id) { saveState = true }
+                                launchSingleTop = true
+                                restoreState = true
+                            }
+                        },
+                        icon = { Icon(Icons.Default.VideoLibrary, contentDescription = null) },
+                        label = { Text("Alle Videos") }
+                    )
+                    NavigationBarItem(
+                        selected = currentRoute == Route.Downloaded.route,
+                        onClick = {
+                            navController.navigate(Route.Downloaded.route) {
+                                popUpTo(navController.graph.findStartDestination().id) { saveState = true }
+                                launchSingleTop = true
+                                restoreState = true
+                            }
+                        },
+                        icon = { Icon(Icons.Default.Download, contentDescription = null) },
+                        label = { Text("Heruntergeladen") }
+                    )
+                }
+            }
+        }
+    ) { innerPadding ->
+        NavHost(
+            navController = navController,
+            startDestination = Route.AllVideos.route,
+            modifier = Modifier.padding(innerPadding)
+        ) {
+            composable(Route.AllVideos.route) {
+                AllVideosScreen(viewModel = viewModel, onVideoClick = { videoId ->
+                    navController.navigate(Route.VideoDetail.createRoute(videoId))
+                })
+            }
+            composable(Route.Downloaded.route) {
+                DownloadedScreen(viewModel = viewModel, onVideoClick = { videoId ->
+                    navController.navigate(Route.VideoDetail.createRoute(videoId))
+                })
+            }
+            composable(
+                route = Route.VideoDetail.route,
+                arguments = listOf(navArgument("videoId") { type = NavType.IntType })
+            ) { backStackEntry ->
+                val videoId = backStackEntry.arguments?.getInt("videoId") ?: return@composable
+                VideoDetailScreen(
+                    videoId = videoId,
+                    viewModel = viewModel,
+                    onPlayClick = { navController.navigate(Route.VideoPlayer.createRoute(videoId)) },
+                    onBackClick = { navController.popBackStack() }
+                )
+            }
+            composable(
+                route = Route.VideoPlayer.route,
+                arguments = listOf(navArgument("videoId") { type = NavType.IntType })
+            ) { backStackEntry ->
+                val videoId = backStackEntry.arguments?.getInt("videoId") ?: return@composable
+                VideoPlayerScreen(videoId = videoId, viewModel = viewModel)
+            }
+        }
+    }
+}
diff --git a/app/frontend/src/main/java/com/youtubeapp/ui/navigation/Routes.kt b/app/frontend/src/main/java/com/youtubeapp/ui/navigation/Routes.kt
new file mode 100644
index 0000000..ab25e1b
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/ui/navigation/Routes.kt
@@ -0,0 +1,12 @@
+package com.youtubeapp.ui.navigation
+
+sealed class Route(val route: String) {
+    object AllVideos : Route("all_videos")
+    object Downloaded : Route("downloaded")
+    object VideoDetail : Route("video_detail/{videoId}") {
+        fun createRoute(videoId: Int) = "video_detail/$videoId"
+    }
+    object VideoPlayer : Route("video_player/{videoId}") {
+        fun createRoute(videoId: Int) = "video_player/$videoId"
+    }
+}
diff --git a/app/frontend/src/main/java/com/youtubeapp/ui/screens/AllVideosScreen.kt b/app/frontend/src/main/java/com/youtubeapp/ui/screens/AllVideosScreen.kt
new file mode 100644
index 0000000..e2754f9
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/ui/screens/AllVideosScreen.kt
@@ -0,0 +1,62 @@
+package com.youtubeapp.ui.screens
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.lazy.grid.GridCells
+import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
+import androidx.compose.foundation.lazy.grid.items
+import androidx.compose.material3.Button
+import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import com.youtubeapp.ui.components.VideoCard
+import com.youtubeapp.ui.viewmodel.VideoViewModel
+
+@Composable
+fun AllVideosScreen(viewModel: VideoViewModel, onVideoClick: (Int) -> Unit) {
+    val state by viewModel.state.collectAsState()
+
+    LaunchedEffect(Unit) {
+        viewModel.loadAllVideos()
+    }
+
+    when {
+        state.isLoading && state.allVideos.isEmpty() -> {
+            Box(Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
+                CircularProgressIndicator()
+            }
+        }
+        state.error != null && state.allVideos.isEmpty() -> {
+            Box(Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
+                Column(horizontalAlignment = Alignment.CenterHorizontally) {
+                    Text("Fehler: ${state.error}")
+                    Button(onClick = { viewModel.loadAllVideos() }) {
+                        Text("Erneut versuchen")
+                    }
+                }
+            }
+        }
+        else -> {
+            LazyVerticalGrid(
+                columns = GridCells.Fixed(2),
+                contentPadding = PaddingValues(8.dp),
+                horizontalArrangement = Arrangement.spacedBy(8.dp),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+                modifier = Modifier.fillMaxSize()
+            ) {
+                items(state.allVideos) { video ->
+                    VideoCard(video = video, onClick = { onVideoClick(video.id) })
+                }
+            }
+        }
+    }
+}
diff --git a/app/frontend/src/main/java/com/youtubeapp/ui/screens/DownloadedScreen.kt b/app/frontend/src/main/java/com/youtubeapp/ui/screens/DownloadedScreen.kt
new file mode 100644
index 0000000..70c5e3c
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/ui/screens/DownloadedScreen.kt
@@ -0,0 +1,67 @@
+package com.youtubeapp.ui.screens
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.lazy.grid.GridCells
+import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
+import androidx.compose.foundation.lazy.grid.items
+import androidx.compose.material3.Button
+import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import com.youtubeapp.ui.components.VideoCard
+import com.youtubeapp.ui.viewmodel.VideoViewModel
+
+@Composable
+fun DownloadedScreen(viewModel: VideoViewModel, onVideoClick: (Int) -> Unit) {
+    val state by viewModel.state.collectAsState()
+
+    LaunchedEffect(Unit) {
+        viewModel.loadDownloadedVideos()
+    }
+
+    when {
+        state.isLoading && state.downloadedVideos.isEmpty() -> {
+            Box(Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
+                CircularProgressIndicator()
+            }
+        }
+        state.error != null && state.downloadedVideos.isEmpty() -> {
+            Box(Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
+                Column(horizontalAlignment = Alignment.CenterHorizontally) {
+                    Text("Fehler: ${state.error}")
+                    Button(onClick = { viewModel.loadDownloadedVideos() }) {
+                        Text("Erneut versuchen")
+                    }
+                }
+            }
+        }
+        state.downloadedVideos.isEmpty() -> {
+            Box(Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
+                Text("Keine heruntergeladenen Videos")
+            }
+        }
+        else -> {
+            LazyVerticalGrid(
+                columns = GridCells.Fixed(2),
+                contentPadding = PaddingValues(8.dp),
+                horizontalArrangement = Arrangement.spacedBy(8.dp),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+                modifier = Modifier.fillMaxSize()
+            ) {
+                items(state.downloadedVideos) { video ->
+                    VideoCard(video = video, onClick = { onVideoClick(video.id) })
+                }
+            }
+        }
+    }
+}
diff --git a/app/frontend/src/main/java/com/youtubeapp/ui/screens/VideoDetailScreen.kt b/app/frontend/src/main/java/com/youtubeapp/ui/screens/VideoDetailScreen.kt
new file mode 100644
index 0000000..923c46f
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/ui/screens/VideoDetailScreen.kt
@@ -0,0 +1,132 @@
+package com.youtubeapp.ui.screens
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.aspectRatio
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material.icons.filled.Download
+import androidx.compose.material.icons.filled.PlayArrow
+import androidx.compose.material3.Button
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedButton
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.SnackbarHost
+import androidx.compose.material3.SnackbarHostState
+import androidx.compose.material3.Text
+import androidx.compose.material3.TopAppBar
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.unit.dp
+import coil.compose.AsyncImage
+import com.youtubeapp.ui.viewmodel.VideoViewModel
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun VideoDetailScreen(
+    videoId: Int,
+    viewModel: VideoViewModel,
+    onPlayClick: () -> Unit,
+    onBackClick: () -> Unit
+) {
+    val state by viewModel.state.collectAsState()
+    val video = viewModel.getVideoById(videoId)
+    val snackbarHostState = remember { SnackbarHostState() }
+
+    LaunchedEffect(state.downloadStatus) {
+        state.downloadStatus?.let { status ->
+            val message = when (status) {
+                "download_started" -> "Download gestartet"
+                "already_downloaded" -> "Bereits heruntergeladen"
+                else -> status
+            }
+            snackbarHostState.showSnackbar(message)
+            viewModel.clearDownloadStatus()
+        }
+    }
+
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text(video?.title ?: "Video") },
+                navigationIcon = {
+                    IconButton(onClick = onBackClick) {
+                        Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = "Zurueck")
+                    }
+                }
+            )
+        },
+        snackbarHost = { SnackbarHost(snackbarHostState) }
+    ) { innerPadding ->
+        if (video == null) {
+            Text("Video nicht gefunden", modifier = Modifier.padding(innerPadding).padding(16.dp))
+        } else {
+            Column(
+                modifier = Modifier
+                    .fillMaxSize()
+                    .padding(innerPadding)
+            ) {
+                AsyncImage(
+                    model = video.thumbnail_url,
+                    contentDescription = video.title,
+                    contentScale = ContentScale.Crop,
+                    modifier = Modifier
+                        .fillMaxWidth()
+                        .aspectRatio(16f / 9f)
+                )
+                Column(modifier = Modifier.padding(16.dp)) {
+                    Text(
+                        text = video.title,
+                        style = MaterialTheme.typography.headlineSmall
+                    )
+                    Spacer(modifier = Modifier.height(4.dp))
+                    Text(
+                        text = video.youtuber,
+                        style = MaterialTheme.typography.bodyLarge,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant
+                    )
+                    Spacer(modifier = Modifier.height(4.dp))
+                    Text(
+                        text = if (video.is_downloaded) "Auf Server heruntergeladen" else "Noch nicht heruntergeladen",
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant
+                    )
+                    Spacer(modifier = Modifier.height(16.dp))
+                    Row(
+                        horizontalArrangement = Arrangement.spacedBy(8.dp),
+                        modifier = Modifier.fillMaxWidth()
+                    ) {
+                        Button(
+                            onClick = onPlayClick,
+                            modifier = Modifier.weight(1f)
+                        ) {
+                            Icon(Icons.Default.PlayArrow, contentDescription = null)
+                            Text("  Abspielen")
+                        }
+                        OutlinedButton(
+                            onClick = { viewModel.triggerDownload(videoId) },
+                            modifier = Modifier.weight(1f)
+                        ) {
+                            Icon(Icons.Default.Download, contentDescription = null)
+                            Text("  Download")
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/app/frontend/src/main/java/com/youtubeapp/ui/screens/VideoPlayerScreen.kt b/app/frontend/src/main/java/com/youtubeapp/ui/screens/VideoPlayerScreen.kt
new file mode 100644
index 0000000..4eeb09b
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/ui/screens/VideoPlayerScreen.kt
@@ -0,0 +1,59 @@
+package com.youtubeapp.ui.screens
+
+import android.app.Activity
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.viewinterop.AndroidView
+import androidx.core.view.WindowCompat
+import androidx.core.view.WindowInsetsCompat
+import androidx.core.view.WindowInsetsControllerCompat
+import androidx.media3.common.MediaItem
+import androidx.media3.exoplayer.ExoPlayer
+import androidx.media3.ui.PlayerView
+import com.youtubeapp.ui.viewmodel.VideoViewModel
+
+@Composable
+@androidx.annotation.OptIn(androidx.media3.common.util.UnstableApi::class)
+fun VideoPlayerScreen(videoId: Int, viewModel: VideoViewModel) {
+    val context = LocalContext.current
+    val streamUrl = viewModel.getStreamUrl(videoId)
+
+    val exoPlayer = remember {
+        ExoPlayer.Builder(context).build().apply {
+            setMediaItem(MediaItem.fromUri(streamUrl))
+            prepare()
+            playWhenReady = true
+        }
+    }
+
+    DisposableEffect(Unit) {
+        val activity = context as? Activity
+        val window = activity?.window
+        val controller = window?.let {
+            WindowCompat.getInsetsController(it, it.decorView)
+        }
+        controller?.let {
+            it.hide(WindowInsetsCompat.Type.systemBars())
+            it.systemBarsBehavior = WindowInsetsControllerCompat.BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE
+        }
+
+        onDispose {
+            exoPlayer.release()
+            controller?.show(WindowInsetsCompat.Type.systemBars())
+        }
+    }
+
+    AndroidView(
+        factory = { ctx ->
+            PlayerView(ctx).apply {
+                player = exoPlayer
+                useController = true
+            }
+        },
+        modifier = Modifier.fillMaxSize()
+    )
+}
diff --git a/app/frontend/src/main/java/com/youtubeapp/ui/theme/Theme.kt b/app/frontend/src/main/java/com/youtubeapp/ui/theme/Theme.kt
new file mode 100644
index 0000000..a622e3c
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/ui/theme/Theme.kt
@@ -0,0 +1,18 @@
+package com.youtubeapp.ui.theme
+
+import android.os.Build
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.darkColorScheme
+import androidx.compose.material3.dynamicDarkColorScheme
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.platform.LocalContext
+
+@Composable
+fun YouTubeAppTheme(content: @Composable () -> Unit) {
+    val colorScheme = if (Build.VERSION.SDK_INT >= 31) {
+        dynamicDarkColorScheme(LocalContext.current)
+    } else {
+        darkColorScheme()
+    }
+    MaterialTheme(colorScheme = colorScheme, content = content)
+}
diff --git a/app/frontend/src/main/java/com/youtubeapp/ui/viewmodel/VideoViewModel.kt b/app/frontend/src/main/java/com/youtubeapp/ui/viewmodel/VideoViewModel.kt
new file mode 100644
index 0000000..ab67104
--- /dev/null
+++ b/app/frontend/src/main/java/com/youtubeapp/ui/viewmodel/VideoViewModel.kt
@@ -0,0 +1,72 @@
+package com.youtubeapp.ui.viewmodel
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import com.youtubeapp.data.Video
+import com.youtubeapp.data.VideoRepository
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.launch
+
+data class VideoUiState(
+    val allVideos: List<Video> = emptyList(),
+    val downloadedVideos: List<Video> = emptyList(),
+    val isLoading: Boolean = false,
+    val error: String? = null,
+    val downloadStatus: String? = null
+)
+
+class VideoViewModel : ViewModel() {
+    private val repository = VideoRepository()
+    private val _state = MutableStateFlow(VideoUiState())
+    val state: StateFlow<VideoUiState> = _state
+
+    fun loadAllVideos() {
+        viewModelScope.launch {
+            _state.value = _state.value.copy(isLoading = true, error = null)
+            repository.getAllVideos()
+                .onSuccess { videos ->
+                    _state.value = _state.value.copy(allVideos = videos, isLoading = false)
+                }
+                .onFailure { e ->
+                    _state.value = _state.value.copy(error = e.message, isLoading = false)
+                }
+        }
+    }
+
+    fun loadDownloadedVideos() {
+        viewModelScope.launch {
+            _state.value = _state.value.copy(isLoading = true, error = null)
+            repository.getDownloadedVideos()
+                .onSuccess { videos ->
+                    _state.value = _state.value.copy(downloadedVideos = videos, isLoading = false)
+                }
+                .onFailure { e ->
+                    _state.value = _state.value.copy(error = e.message, isLoading = false)
+                }
+        }
+    }
+
+    fun triggerDownload(videoId: Int) {
+        viewModelScope.launch {
+            _state.value = _state.value.copy(downloadStatus = null)
+            repository.triggerDownload(videoId)
+                .onSuccess { status ->
+                    _state.value = _state.value.copy(downloadStatus = status)
+                }
+                .onFailure { e ->
+                    _state.value = _state.value.copy(downloadStatus = "Fehler: ${e.message}")
+                }
+        }
+    }
+
+    fun clearDownloadStatus() {
+        _state.value = _state.value.copy(downloadStatus = null)
+    }
+
+    fun getVideoById(videoId: Int): Video? {
+        return _state.value.allVideos.find { it.id == videoId }
+    }
+
+    fun getStreamUrl(videoId: Int): String = repository.getStreamUrl(videoId)
+}
diff --git a/app/gradle.properties b/app/gradle.properties
index 32a0c14..3ac72d6 100644
--- a/app/gradle.properties
+++ b/app/gradle.properties
@@ -1,3 +1,4 @@
 android.useAndroidX=true
 kotlin.code.style=official
 org.gradle.jvmargs=-Xmx2048m
+org.gradle.java.home=/usr/lib/jvm/java-17-openjdk-amd64