Hi Imad,

First thing to do is check for leaks underneath. Park on a clean, dry, flat piece of ground and leave the car run for a few minutes. Inspect the ground for oil and if there is an obvious leak, then try to see where it is before you bring the car to a mechanic to remedy it. 

If it's not a leak, and the engine is burning oil, then it may be more difficult to diagnose, and you really should employ the services of a good mechanic to get to the bottom of it, in case the issue worsens and causes expensive damage to the engine.