OP, I absolutely sympathize with your situation and getting scammed to the point where you're in mental agony shouldn't happen to anyone, but why do you think anyone on bitcointalk would have any influence on gate.io?  You've already reported the problem here for the community to see, so if they were at all concerned about their reputation (and if what you say is true), they'd rectify the situation immediately.

Not sure how much lawyers go for where you live in Serbia, but I'd think generally for $9000 it wouldn't be worth the cost of hiring a lawyer, because you'd probably only recovery 1/3 or less of that.  Maybe you could get one to take your case on a near pro bono rate, but somehow I doubt that.

Anyway, I wish you luck in getting your money back.