Audi A3 no handbrake and all the lights are on the dash. Can't find problem with diagnostic check as failing everything.

SOURCE: Reverse lights not working.

Most likely. It sits on the front of the gearbox and has 2 wires going into it. Remove the plug and bridge the wires with a small piece of insulated wire. Turn ignition on. If lights are on change the switch
Cheers John

SOURCE: Intermittant misfire Audi A3 1.8T (1999)

Sounds like carbon build-up in the cylinders. Take it and have it put on a machine called a "Motor-Vac"

SOURCE: Audi A3 hazard lights keep flashing when parked. I

is the switch fully depressed ? otherwise most likely faulty switch

SOURCE: AUDI A3 intake flag motor

I had the exact same problem. The check engine light would come on then go off. I didn't notice any drivabiltiy issues. End the end I had to replace the flapper motor, the high pressure fuel pump and the camshaft. They showed me the old parts and sure enough the camshaft lobe was worn down and the cam follower that actuates the fuel pump was in pieces. Needless to say it was very expensive. It's been a problem posted on many Audi sites. I went ahead and had the timing belt changed. Now she's as good as new.

SOURCE: how to adust audi a3 door, it has dropped about

if hinges are in good order, then ,with the door ajar "adjust" by grabbing hold of the bottom of the door edge and lifting upwards a little at a time to get correct fit,a common problem with heavy doors nowadays....