I think I found the problem, and I hope you will help me.
first question: the size "gb or mb" of an object is important?
this is what i saw this morning !
the first photo I imported the piece but divided it in half, and the piece is perfect now, the second photo imported it complete and that's what happens... I forgot imported both pieces in the same way
I also noticed, that when I put so many pieces to cover everything I have to put the texture to 8k and only in that way covers everything, and then I bring them back in 4k even if a little ruins it... how can fix it?
in other words if I want to paint everything well I have to have everything in 8k and I think this is impossible for a game load lots of textures in 8k at the same time