Thanks for the comment. Me and my friend developed the game. we couldn't find a good idea for the theme. Then we said lets make a simple multiplayer game, at least we learn something. But we couldn't finish it in time.
Sorry everyone, we were not able to set up a proper server in time so we setup a server on our local pc with a hard coded join. Later the server is shutdown probably because of inactivity and we cant fix the issue without an update to the game.