i was wondering if its possible in map editor to make custom mech fight each other

Yep! You can change the side the mechs are on at the top of their details panel when you click one in the map editor (player/AI enemy/AI ally/none). The AI isn’t great at using all player systems, though.

when i try to spawn my mech's the game ends

Could you give me any more details? I just did a quick test and yeah it does look like you need at least one player-controlled unit on the field or it’ll wrap up after a round or two. Is that what you’re seeing?

that my problem it wraps for round one to two then ends

how do i make that after i kill the mech the match ends