How do i create an party to players enter to get teleported to game?

In Escape Room there are different maps and you can create your party to players join. The max players are 7. I wanna make a GUI that when you click you can create a party to other's join and name it. The players need leave party. When party is full game starts and they are teleported to Lobby in the lobby they wait game starts to be teleported to map "Map is inside this game". In this Map there's murderer and surivors no one know who is. When murderer wins they will be teleported to other place that is where you create a party if surivors win the same happen.