i met yesterday ,some players that doesnt know how to play on that server , a little explanation can be usefull :

First, when you spawn , you will have no weapon.In front of you there will be four portals,each portal leads to an arena, with a specific gametype and config.This way you can have 20 people on the same map, but some play FFA,and some others 1v1, in different rooms.

If you want to go back to the first spawn room, click on "Escape"; then "arena" ( a new button that normally doesnt show on E+), and you spawn back where you started and you can choosee a new arena again.

One example : In arena 1, there is a rail only config,with TDM gametype , but blocked at 3 players each team.because of the size of the map.Muti arena, allows you to configurate very precisely every aspect of each arena.

Have fun.