idling goes up and down

Hi yes this sounds like a timing problem recheck the timing belt

Hi! Billymac, you mean the timing is out maybe by one tooth or what must I check exacly?

Yes mostlikely it is out by one tooth this will cause these issues you have. maybe not but we have to start there

Thank you very much Billymac I got assistance from someone to set the timing for me and there is a big improvement but the idling is still not stable, when I start the car it idles at 1000 rev/min and slowly goes below 1000 rev/min as the car idles. There is one more thing that I don't understand now, the car can't drive smoothly at take offs especially at gear 1 when I release the clutch pedal without pressing the gas pedal it hesitate like and the engine goes off.Is it still timing problem? What can be the problem Sir?.

it really sounds like you still have a small timeing prob possibly a misplaced vac hose

The ignition timing is not adjustable. If it overheated, then you need to have the cooling system pressure tested to find the leak. The reason it's not idling right is likely because it's low on coolant. The IAC (idle air control) works off coolant temp and if it's low it will have air pockets that don't read.