ANSWER:

If you can see him, move as soon as he reaches the position he is moving to whether he says the takbeer or not. But if you can’t see him, You should follow him after he finishes the takbeer.

QUESTION: Sheikh I know that you are supposed to follow the imam in salat but in my masjid in subcontinent the imam changes the position then says the moving takbir and everyone follows him and I sometimes get confused and bend my knees a little then wait am I sinful