I'm not Teropa, but...
...(and I hope you are being sincere here), with so little to go on, it is almost impossible to say what your problem is. If you could tell us what aircraft you are trying to land, where and what shape you are trying to land it in (Speed, flaps, weight, weather, type of approach, etc...) we might be able to help.
First thing I would suggest you look at (especially if trying to fly an airliner) is weight. Flightsim will, by default, start you with full tanks. If you want to take-off, fly a cuircuit and land, off-load some fuel first. You wouldn't do it in your Airbus with full tanks, would you?
Rgds,
Hippy.