diff --git a/lib/src/providers/api/api.dart b/lib/src/providers/api/api.dart
index 097fed6..1ddfa75 100644
--- a/lib/src/providers/api/api.dart
+++ b/lib/src/providers/api/api.dart
@@ -130,7 +130,7 @@ Future uploadMediaFile(
 
   int offset = box.get("retransmit-$messageId-offset") ?? 0;
 
-  int fragmentedTransportSize = 50000;
+  int fragmentedTransportSize = 1_000_000; // per upload transfer
 
   while (offset < encryptedMedia.length) {
     Logger("api.dart").info("Uploading image $messageId with offset: $offset");
@@ -272,6 +272,7 @@ Future sendImage(
 Future tryDownloadMedia(int messageId, int fromUserId, List<int> mediaToken,
     {bool force = false}) async {
   if (globalIsAppInBackground) return;
+
   if (!force) {
     // TODO: create option to enable download via mobile data
     final List<ConnectivityResult> connectivityResult =
@@ -281,9 +282,15 @@ Future tryDownloadMedia(int messageId, int fromUserId, List<int> mediaToken,
       return;
     }
   }
+
+  final box = await getMediaStorage();
+  if (box.containsKey("${mediaToken}_downloaded")) {
+    Logger("tryDownloadMedia").shout("mediaToken already downloaded");
+    return;
+  }
+
   Logger("tryDownloadMedia").info("Downloading: $mediaToken");
   int offset = 0;
-  final box = await getMediaStorage();
   Uint8List? media = box.get("$mediaToken");
   if (media != null && media.isNotEmpty) {
     offset = media.length;
diff --git a/lib/src/providers/api/server_messages.dart b/lib/src/providers/api/server_messages.dart
index 736df6c..636d499 100644
--- a/lib/src/providers/api/server_messages.dart
+++ b/lib/src/providers/api/server_messages.dart
@@ -1,7 +1,6 @@
 import 'dart:convert';
 import 'dart:typed_data';
 import 'package:fixnum/fixnum.dart';
-import 'package:flutter/foundation.dart';
 import 'package:libsignal_protocol_dart/libsignal_protocol_dart.dart';
 import 'package:logging/logging.dart';
 import 'package:twonly/globals.dart';
diff --git a/lib/src/providers/api_provider.dart b/lib/src/providers/api_provider.dart
index 577507e..2b4d4ef 100644
--- a/lib/src/providers/api_provider.dart
+++ b/lib/src/providers/api_provider.dart
@@ -25,11 +25,11 @@ import 'package:web_socket_channel/web_socket_channel.dart';
 /// It handles errors and does automatically tries to reconnect on
 /// errors or network changes.
 class ApiProvider {
-  final String apiUrl = (kDebugMode && false)
+  final String apiUrl = (kDebugMode)
       ? "ws://10.99.0.6:3030/api/client"
       : "wss://api.twonly.eu/api/client";
   // ws://api.twonly.eu/api/client
-  final String? backupApiUrl = (kDebugMode && false)
+  final String? backupApiUrl = (kDebugMode)
       ? "ws://10.99.0.6:3030/api/client"
       : "wss://api2.twonly.eu/api/client";
   bool isAuthenticated = false;
diff --git a/lib/src/providers/messages_change_provider.dart b/lib/src/providers/messages_change_provider.dart
index 8ee89c6..93fa0b9 100644
--- a/lib/src/providers/messages_change_provider.dart
+++ b/lib/src/providers/messages_change_provider.dart
@@ -34,6 +34,8 @@ class MessagesChangeProvider with ChangeNotifier, DiagnosticableTreeMixin {
         int index = _allMessagesFromUser[targetUserId]!
             .indexWhere((x) => x.messageId == messageId);
         if (index == -1) {
+          print("should be indexed by time!!");
+
           _allMessagesFromUser[targetUserId]!.insert(0, msg);
           // reload all messages but async
           loadMessagesForUser(targetUserId, force: true);
diff --git a/lib/src/utils/signal.dart b/lib/src/utils/signal.dart
index 3837444..e2452c0 100644
--- a/lib/src/utils/signal.dart
+++ b/lib/src/utils/signal.dart
@@ -49,22 +49,20 @@ Future<bool> addNewContact(Response_UserData userData) async {
         1);
     tempPreKeyId = userData.prekeys.first.id.toInt();
   }
-  // Signed pre key calculation
+
   int tempSignedPreKeyId = userData.signedPrekeyId.toInt();
-  // Map? tempSignedPreKey = remoteBundle["signedPreKey"];
-  ECPublicKey? tempSignedPreKeyPublic;
-  Uint8List? tempSignedPreKeySignature;
-  // if (tempSignedPreKey != null) {
-  tempSignedPreKeyPublic = Curve.decodePoint(
+
+  ECPublicKey? tempSignedPreKeyPublic = Curve.decodePoint(
       DjbECPublicKey(Uint8List.fromList(userData.signedPrekey)).serialize(), 1);
-  tempSignedPreKeySignature =
+
+  Uint8List? tempSignedPreKeySignature =
       Uint8List.fromList(userData.signedPrekeySignature);
-  // }
-  // Identity key calculation
+
   IdentityKey tempIdentityKey = IdentityKey(Curve.decodePoint(
       DjbECPublicKey(Uint8List.fromList(userData.publicIdentityKey))
           .serialize(),
       1));
+
   PreKeyBundle preKeyBundle = PreKeyBundle(
     userData.userId.toInt(),
     1,
@@ -230,6 +228,7 @@ Future<Uint8List?> decryptBytes(Uint8List bytes, Int64 target) async {
     int type = bytesToInt(msgs[1]);
 
     Uint8List plaintext;
+    Logger("utils/signal").info("got signal type: $type!");
     if (type == CiphertextMessage.prekeyType) {
       PreKeySignalMessage pre = PreKeySignalMessage(body);
       plaintext = await session.decrypt(pre);
@@ -237,6 +236,7 @@ Future<Uint8List?> decryptBytes(Uint8List bytes, Int64 target) async {
       SignalMessage signalMsg = SignalMessage.fromSerialized(body);
       plaintext = await session.decryptFromSignal(signalMsg);
     } else {
+      Logger("utils/signal").shout("signal type is not known: $type!");
       return null;
     }
     List<int>? plainBytes = gzip.decode(Uint8List.fromList(plaintext));
diff --git a/pubspec.yaml b/pubspec.yaml
index 60b7a36..b28914c 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -7,7 +7,7 @@ publish_to: 'none'
 version: 0.0.4+4
 
 environment:
-  sdk: ^3.5.4
+  sdk: ^3.6.0
 
 dependencies:
   camerawesome: ^2.1.0