got my self audi 01, a4 b5. 1.8 not turbo. and it came with few problems!!!!!. its done around 260,000 km got it all the filters changed, engine oil as well!

1.my airbag sign is flashing one time, its sometimes totally off and another time stays on, wtf? yes i tried fixing it, the cables under the seat disconnected them and connected them again, stayed off for a while and came back on?? i have no clue what to do??

2. this is giant problem when i turn on my car especially in the morning and ride up my hilly driveway the exhaust is making rattling sounds like got rocks in it or got a hole in it, the thing is its fine!! i went to change the whole exhaust system and they said it was ok. today i was outside turned the car on and revved it few times then some oil came out, it was black it had a lil bit of water with it, it’s only when im driving that the exhaust is sounding crap and hallow, when im stationary and revving it, it sounds normal expect the oil and a lil smell of petrol coming out, this might also be the cause why im getting like 400 km per tank :S is that normal and im not a crazy driver??

3. my stupid comp screens is showing that my light isnt working, when it is, amongst other things??? how can i reset it or turn the dam thing back to normal??? man i seriously need some advice!! thank you in advance so much!!