Electrical Problem

I have a 1997 golf 3 gti. i just bought it from a guy who ripped me off and stuff. he said it just a loose ground wire some where. my srs airbag light is on and abs light is on as well. when i take off the hand brake my head lights turns on and my signal does no signal at all. My back and reverse light dont light up even though the bulbs not burnt help plz anyone who know or experienced this situation thanks.