HELP 1999 Audi 1.8 8L Locking / Alarm Issue

Hello, 

I am very new to the forum and Audi ownership. 

Just purchased a 1999 Audi A3 1.8 Sport.

Have a very very annoying issue with the hazards and locking.. here goes..

I lock the car via the drivers side and everything locks. Come back and I open the car and only the drivers side opens. No boot or passenger door. Drivers door lock button is unresponsive. Doesn’t matter what I do next, the hazard lights go mad if I try and start the car or even get in it. I have to pop the bonnet and disconnect the battery and reconnect. Then and only then will the drivers side lock button work to open the rest of the doors and allow me to continue hazard light free. Very weird. Abit of background the car is old obviously and was sitting for a few years. The battery terminals and fuse box type component on top are loose due to messed up nuts and bolts and snapped hinges due to someone not knowing what they were doing (this car was meant to have been a mechanics “baby” for the last 11 years which has been maintained super well, slowing realising not the case) So while I have been driving about and its skipping about the place I’ve had starting issues (no power that became obvious, had a red flashing warning light like (!) and ABS warning appear. Bodged the battery for time being and no more appearances from them so I am hoping that is solved. For some who are probably thinking “you ****” for purchasing this car for any reason, the seller was a friend of a trusted party and I took their word for it and take responsibility for not doing checks I would have otherwise done. 

Sorry to ramble, hope to hear from someone, could do with the help!

Cheers!