What is wrong with my Volkswagen Golf GTI tail lights?

Hello. I just bought a set of aftermarket tail lights for my 2000 Volkswagen golf. The lights fit great, but the only thing that wont work is the brake lights. They will either not light up at all with the headlights on, or will illuminate all of the brake lights even without the brake on. I am not sure what I should do. Should I try and move the running light wire to another housing because one of the housings won't do anything. Thanks.|||try putting the stock ones back in to figure out if its the new lights or just the wiring