xxx15 install... BIG problems

[forbidden 10+ year member]

You and your friend have just proven to be a further reason to the existence of stores like mine. No offence intended but you should not be fooling around with electronics or electrical system based on the things that you have just said. Before you actually damage either the amp or the car / system, stop right now and take it to a shop before the potential for damage and the repairs associated to it outweigh the costs to get it looked after properly.