What we should do to get out from the trap? How high are our chances to win the case?

Not high at all, you live in an apartment it's your own fault.. noise complaints if made by more then one person should be brought to the attention of the guy your renting from or girl w.e A judge most likely won't take your case seriously and will just write you off most likely. It's a apartment to people issue not a legal issue. Your only option is to one move out or two get the person you rent from to kick the other person out.