You can easily take a map and just spawn additional players. But everything else is up to you. UE can’t decide what shall happen if two guys meet online.
You can launch your single player game as server or listen server just by adding a command line argument to the executable. But I don’t think the netcode can handle thousands of clients straight out of the box.
Thanks for the info
but what can i do if i for example release an online game for everybody and if for example 10 players in 1game, can other players start another game so that there are 100 peoples are playing multiple games without any problems?