diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 41ae4ce7f..2298b6284 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -52,8 +52,8 @@
     <uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />
     <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
     <uses-permission android:name="android.permission.VIBRATE" />
-    <uses-permission android:name="android.permission.USE_FULL_SCREEN_INTENT"/>
-    <uses-permission android:name="android.permission.FOREGROUND_SERVICE"/>
+    <uses-permission android:name="android.permission.USE_FULL_SCREEN_INTENT" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
     <uses-permission android:name="android.permission.READ_CONTACTS" />
     <uses-permission android:name="android.permission.WRITE_CONTACTS" />
     <uses-permission android:name="android.permission.READ_PROFILE" />
@@ -79,6 +79,8 @@
     <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
     <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
 
+    <uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS" />
+
     <application
         android:name=".application.NextcloudTalkApplication"
         android:allowBackup="true"
@@ -87,9 +89,9 @@
         android:label="@string/nc_app_name"
         android:largeHeap="true"
         android:networkSecurityConfig="@xml/network_security_config"
+        android:requestLegacyExternalStorage="true"
         android:supportsRtl="true"
         android:theme="@style/AppTheme.Launcher"
-        android:requestLegacyExternalStorage="true"
         tools:ignore="UnusedAttribute"
         tools:replace="label, icon, theme, name, allowBackup">
 
@@ -127,41 +129,38 @@
 
         <activity
             android:name=".activities.CallActivity"
-            android:theme="@style/AppTheme.CallLauncher"
-            android:supportsPictureInPicture="true"
             android:configChanges="screenSize|smallestScreenSize|screenLayout|orientation"
-            android:launchMode="singleTask"
-            android:taskAffinity=".call"
             android:excludeFromRecents="true"
-            android:showOnLockScreen="true"/>
+            android:launchMode="singleTask"
+            android:showOnLockScreen="true"
+            android:supportsPictureInPicture="true"
+            android:taskAffinity=".call"
+            android:theme="@style/AppTheme.CallLauncher" />
 
         <activity
             android:name=".activities.CallNotificationActivity"
-            android:theme="@style/AppTheme.CallLauncher"
-            android:supportsPictureInPicture="true"
             android:configChanges="screenSize|smallestScreenSize|screenLayout|orientation"
-            android:launchMode="singleTask"
-            android:taskAffinity=".call"
             android:excludeFromRecents="true"
-            android:showOnLockScreen="true" />
+            android:launchMode="singleTask"
+            android:showOnLockScreen="true"
+            android:supportsPictureInPicture="true"
+            android:taskAffinity=".call"
+            android:theme="@style/AppTheme.CallLauncher" />
 
         <activity
             android:name=".activities.FullScreenImageActivity"
-            android:theme="@style/FullScreenImageTheme"
-            android:configChanges="orientation|keyboardHidden|screenSize">
-        </activity>
+            android:configChanges="orientation|keyboardHidden|screenSize"
+            android:theme="@style/FullScreenImageTheme"></activity>
 
         <activity
             android:name=".activities.FullScreenMediaActivity"
-            android:theme="@style/FullScreenMediaTheme"
-            android:configChanges="orientation|keyboardHidden|screenSize">
-        </activity>
+            android:configChanges="orientation|keyboardHidden|screenSize"
+            android:theme="@style/FullScreenMediaTheme"></activity>
 
         <activity
             android:name=".activities.FullScreenTextViewerActivity"
-            android:theme="@style/FullScreenTextTheme"
-            android:configChanges="orientation|keyboardHidden|screenSize">
-        </activity>
+            android:configChanges="orientation|keyboardHidden|screenSize"
+            android:theme="@style/FullScreenTextTheme"></activity>
 
         <activity
             android:name=".activities.TakePhotoActivity"
@@ -170,7 +169,7 @@
 
         <activity
             android:name=".shareditems.activities.SharedItemsActivity"
-            android:theme="@style/AppTheme"/>
+            android:theme="@style/AppTheme" />
 
         <receiver android:name=".receivers.PackageReplacedReceiver">
             <intent-filter>
diff --git a/app/src/main/java/com/nextcloud/talk/controllers/ConversationsListController.java b/app/src/main/java/com/nextcloud/talk/controllers/ConversationsListController.java
index dfb72b333..000a61942 100644
--- a/app/src/main/java/com/nextcloud/talk/controllers/ConversationsListController.java
+++ b/app/src/main/java/com/nextcloud/talk/controllers/ConversationsListController.java
@@ -93,6 +93,7 @@ import com.nextcloud.talk.utils.DisplayUtils;
 import com.nextcloud.talk.utils.UriUtils;
 import com.nextcloud.talk.utils.bundle.BundleKeys;
 import com.nextcloud.talk.utils.database.user.UserUtils;
+import com.nextcloud.talk.utils.power.PowerManagerUtil;
 import com.nextcloud.talk.utils.preferences.AppPreferences;
 import com.webianks.library.PopupBubble;
 import com.yarolegovich.lovelydialog.LovelySaveStateHandler;
@@ -253,6 +254,10 @@ public class ConversationsListController extends BaseController implements Searc
 
         adapter.addListener(this);
         prepareViews();
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+            new PowerManagerUtil().askForBatteryOptimization(getActivity());
+        }
     }
 
     private void loadUserAvatar(MaterialButton button) {
@@ -427,8 +432,8 @@ public class ConversationsListController extends BaseController implements Searc
                     MainActivity activity = (MainActivity) getActivity();
                     if (activity != null) {
                         activity.binding.appBar.setStateListAnimator(AnimatorInflater.loadStateListAnimator(
-                            activity.binding.appBar.getContext(),
-                            R.animator.appbar_elevation_off)
+                                                                         activity.binding.appBar.getContext(),
+                                                                         R.animator.appbar_elevation_off)
                                                                     );
                         activity.binding.toolbar.setVisibility(View.GONE);
                         activity.binding.searchToolbar.setVisibility(View.VISIBLE);
@@ -644,8 +649,8 @@ public class ConversationsListController extends BaseController implements Searc
             List<AbstractFlexibleItem> openConversationItems = new ArrayList<>();
 
             openConversationsQueryDisposable = ncApi.getOpenConversations(
-                credentials,
-                ApiUtils.getUrlForOpenConversations(apiVersion, currentUser.getBaseUrl()))
+                    credentials,
+                    ApiUtils.getUrlForOpenConversations(apiVersion, currentUser.getBaseUrl()))
                 .subscribeOn(Schedulers.io())
                 .observeOn(AndroidSchedulers.mainThread())
                 .subscribe(roomsOverall -> {
@@ -690,7 +695,7 @@ public class ConversationsListController extends BaseController implements Searc
                     if (getParentController() != null && getParentController().getRouter() != null) {
                         Log.d(TAG, "Starting reauth webview via getParentController()");
                         getParentController().getRouter().pushController((RouterTransaction.with
-                            (new WebViewLoginController(currentUser.getBaseUrl(), true))
+                                (new WebViewLoginController(currentUser.getBaseUrl(), true))
                             .pushChangeHandler(new VerticalChangeHandler())
                             .popChangeHandler(new VerticalChangeHandler())));
                     } else {
@@ -1178,7 +1183,7 @@ public class ConversationsListController extends BaseController implements Searc
                             onAttach(getView());
                         } else if (!otherUserExists) {
                             getRouter().setRoot(RouterTransaction.with(
-                                new ServerSelectionController())
+                                    new ServerSelectionController())
                                                     .pushChangeHandler(new VerticalChangeHandler())
                                                     .popChangeHandler(new VerticalChangeHandler()));
                         }
@@ -1188,7 +1193,7 @@ public class ConversationsListController extends BaseController implements Searc
                     @Override
                     public void onClick(View v) {
                         getRouter().pushController(RouterTransaction.with(
-                            new WebViewLoginController(currentUser.getBaseUrl(), true))
+                                new WebViewLoginController(currentUser.getBaseUrl(), true))
                                                        .pushChangeHandler(new VerticalChangeHandler())
                                                        .popChangeHandler(new VerticalChangeHandler()));
                     }
@@ -1221,7 +1226,7 @@ public class ConversationsListController extends BaseController implements Searc
                         onAttach(getView());
                     } else if (!otherUserExists) {
                         getRouter().setRoot(RouterTransaction.with(
-                            new ServerSelectionController())
+                                new ServerSelectionController())
                                                 .pushChangeHandler(new VerticalChangeHandler())
                                                 .popChangeHandler(new VerticalChangeHandler()));
                     }
diff --git a/app/src/main/java/com/nextcloud/talk/utils/power/PowerManagerUtil.kt b/app/src/main/java/com/nextcloud/talk/utils/power/PowerManagerUtil.kt
new file mode 100644
index 000000000..e4634baab
--- /dev/null
+++ b/app/src/main/java/com/nextcloud/talk/utils/power/PowerManagerUtil.kt
@@ -0,0 +1,57 @@
+package com.nextcloud.talk.utils.power
+
+import android.annotation.SuppressLint
+import android.content.Context
+import android.content.Context.POWER_SERVICE
+import android.content.Intent
+import android.net.Uri
+import android.os.Build
+import android.os.PowerManager
+import android.provider.Settings
+import androidx.annotation.RequiresApi
+import androidx.appcompat.app.AlertDialog
+import androidx.lifecycle.LifecycleObserver
+import com.nextcloud.talk.BuildConfig
+import com.nextcloud.talk.R
+
+class PowerManagerUtil : LifecycleObserver {
+
+    @RequiresApi(Build.VERSION_CODES.M)
+    fun askForBatteryOptimization(context: Context) {
+        if (checkIfBatteryOptimizationEnabled(context)) {
+            val alertDialogBuilder = AlertDialog.Builder(context, R.style.Theme_ownCloud_Dialog)
+                .setTitle("Battery optimization")
+                .setMessage(
+                    "Your device may have battery optimization enabled. Notifications work only properly if " +
+                        "you exclude this app from it."
+                )
+                .setPositiveButton("disable") { _, _ ->
+                    @SuppressLint("BatteryLife") val intent = Intent(
+                        Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS,
+                        Uri.parse("package:" + BuildConfig.APPLICATION_ID)
+                    )
+                    context.startActivity(intent)
+                }
+                .setNeutralButton("close") { dialog, _ -> dialog.dismiss() }
+            alertDialogBuilder.show()
+        }
+    }
+
+    /**
+     * Check if battery optimization is enabled. If unknown, fallback to true.
+     *
+     * @return true if battery optimization is enabled
+     */
+    @RequiresApi(Build.VERSION_CODES.M)
+    private fun checkIfBatteryOptimizationEnabled(context: Context): Boolean {
+        val powerManager = context.getSystemService(POWER_SERVICE) as PowerManager?
+        return when {
+            powerManager != null -> !powerManager.isIgnoringBatteryOptimizations(BuildConfig.APPLICATION_ID)
+            else -> true
+        }
+    }
+
+    companion object {
+        private val TAG = PowerManagerUtil::class.simpleName
+    }
+}
diff --git a/app/src/main/res/values/styles.xml b/app/src/main/res/values/styles.xml
index d16b13034..d7ed97275 100644
--- a/app/src/main/res/values/styles.xml
+++ b/app/src/main/res/values/styles.xml
@@ -122,6 +122,27 @@
         <item name="iconTint">@color/fontAppbar</item>
     </style>
 
+    <!-- Dialogs -->
+    <style name="Theme.ownCloud.Dialog" parent="@style/Theme.MaterialComponents.DayNight.Dialog.Alert">
+        <item name="windowNoTitle">false</item>
+        <item name="colorAccent">@color/colorAccent</item>
+        <item name="android:windowBackground">@color/bg_default</item>
+        <item name="android:textAllCaps">false</item>
+        <item name="textInputStyle">@style/Widget.App.TextInputLayout</item>
+    </style>
+
+    <style name="Widget.App.TextInputLayout" parent="Widget.MaterialComponents.TextInputLayout.OutlinedBox">
+        <item name="materialThemeOverlay">@style/ThemeOverlay.App.TextInputLayout</item>
+        <item name="hintTextColor">?attr/colorOnSurface</item>
+    </style>
+
+    <style name="ThemeOverlay.App.TextInputLayout" parent="ThemeOverlay.MaterialComponents.TextInputEditText.OutlinedBox">
+        <item name="colorPrimary">@color/colorPrimary</item>
+        <item name="colorOnSurface">@color/colorPrimary</item>
+        <item name="colorError">@color/hwSecurityRed</item>
+        <item name="editTextStyle">@style/Widget.MaterialComponents.TextInputEditText.OutlinedBox</item>
+    </style>
+
     <style name="menuTextAppearance" parent="TextAppearance.AppCompat.Widget.ActionBar.Menu">
         <item name="android:textAllCaps">false</item>
     </style>