it's impossible to lower it on the top of the building. it stops at a few feet in the air.

Objects can’t have a negative elevation in their level, the reason why your roof items should be moved to a lower level.

Also when moving it, it moves by itself and sticks to some imaginary guide line that do not exist. I am having a nightmare

Learn how to control magnetism in Sweet Home 3D and your nightmares will become sweet dreams.