Multiplayer Achievement Help - 360

Returned to the 360 after a couple years and started working on Borderlands and i could really use some help,
I got 3 achievements i need help on which are…

Can’t We Get BEYOND Thunderdome? - Win an arena match

There’s No “I” In “Team” - Complete 15 missions in co-op

And They’ll Tell Two Friends - Play in a co-op game with either an employee of Gearbox or someone who has this achievement

GT: Llehctim

still need help? my gamertag is PeterL2014. I can help get these achievements

I can help. BigSmooth514.