Tank is standing at initial position and NOT falling

At the beginnig of the game, tank need to fall into the ground and etc… But After this lecture’s changes, my tank is steady. It has not felt into the ground. All other functionalities are okay (like firing etc).

It seems like my tank in stuck in its initial position. When I play the game and then press F8. I ve tried to change its position but tank always go back its initial position again. (just like a spring)

And When I finally quit from the game I ve got following errors.

Have you pushed your recent changes?

Yes I commited my last works. Here.

You have several merge conflicts in your code

And more.