Retake on Haven

Hey guys, I am currently Plat 2 and I play with a duo or trio most of the time. We always struggle to retake any site except for maybe B on Haven. Are their tricks or tips or do we just need to win our gunfights better?

Just for example say it’s 3v4 and they take C on haven. Is the trick sending someone from CT to flank from T side?

Thanks in advance for any answers or ideas