After stopping gear box does not engage

I do not understand what you are saying, you said, "if the car stops the gear box does not engage and stop moving". When the car comes to a stop the gear box (transmission) should not engage, and it should stop moving.

So what you are saying after coming to a stop, then trying to move forward again in gear, that the vehicle and transmission will not move forward, but it does move if you jack up the front wheels until they are off the ground.
If so, the first thing I would do is check the transmission fluid level and condition, meaning it does not smell burnt or look brown and that it is full.
If all is okay with the fluid, remove the transmission fluid pan and make sure the filter is not clogged up with debris that has fallen off clutch packs within the transmission and clean the pan out, replace the filter, install a new pan gasket, then top back off with fluid and now check it.
If still no movement, at least have the trouble codes retrieved from the computer modules to see if anything refers to the transmission and then if so post those trouble codes in here.