Now i got VAC banned again

Don't team up with friends you barely know or know very little. They might be tempted to try a cheat and you might get VAC'ed too, if you're in the same group in the lobby when queuing up for a game.

Be especially careful when accepting friend requests and then playing with those people. Never queue for a game with barely known people. Because a VAC ban is permanent and it's also a mark on your account.

Also, good advice would be to record yourself when playing with new people, with stuff like NVIDIA Shadowplay, especially if you got potato aim, to secure yourself against getting VAC'ed mistakenly. Might not do much, but still it's something. And something is better than nothing.