Remember I use the form designer, Yousfi, and don't code everything by hand like you do!
This is in the beginning of Main.prg:
_screen.closable=.f.
_screen.maxbutton=.f.
_screen.Minbutton=.f.
_screen.controlbox=.f.
_screen.Visible=.f.

This is the only thing in the config.fpw:
screen=off