Is it possible to add more teams than 1,2 (Which are already made..) and 3.
I have tryed and failed many times to get at least 4 teams
(I take 3rd team Script stuff, Copy it and change around names. ((As in locols to boss))

You have to add a spawn point for this new team in ZeroEdit as well, otherwise they have nowhere to spawn in the map...

I've never done it, but I assume it would just be an invisible (or hidden) uncapturable command post model and set the field that determines which team can spawn to 4.

I remember reading that there can be up to 9(?) teams, but I'm not 100% on that.

You can only have 2 playable teams.

If you want to add more AI teams, see this, a part of it describes how to add another team.

And yes, 9 teams total is the limit.