variuos electrical problems on my clio 172?

i recently bought a clio 172 sport(2002) last week and knew there were couple of electrical faults,

1. The speedo works say 75% then just goes back to 0 and offcourse messes up all the readings and doesnt include the mileage when it does this too!!

2. The airbag light always flicks on and off throughout a journey which is annoying

3.after a while driving a light comes on below the fuel one,im thinking electric light and it goes into home safe mode and allows me to rev up to 2500rpm intill i start the car again and it turns off

4.the bottom right light,i think its toxic/gas light comes on too and stays on,id say its on half the time

what can i do about all of these?

i dont want to take it to my local renault as they have just been fined 30k for saying they carried out jobs when they didnt!!!!