Hello I am trying to create a multiplayer game where if all player except one (the winner of the round) are dead the Mapof the session is changing. I have already a Datatable with all my Maps but I have no clue how i can change the Map or how to check if all Player are still alive. Any kind of help would be great 
simple approach…
Create a custom playerstate class. You’ll want one eventually anyway.
To track players alive status you need to create a variable in the PlayerState (e.g. IsAlive[bool] ). On round start or pre-start use GameState to Loop through PlayerArray and Set everyone’s IsAlive to 1.
On death you update the playerstate IsAlive to 0 on the player that just died, then immediately have the GS loop though and get a count of total alive. If == 1, then only one is alive and you can call a map change.