Audi CD changer and noise

I own Audi a4 1999 79000mi 1.8 turbo. I have recently changed battery after which the cd changer is not communicating with radio, cassette and stations are working but cd is not an error apears "no cdc" another problem I have is noise coming from the drivers side, when pressing the break and when accelerating or hitting a bump on the road. It is very strange noise and hard to describe but it sound like creaking doors. If somebody could help me I would be greatefull thanks.