demm Ok i fixed the problem , i have removed amdgpu because it has a problem with xorg it requires newer version or something.
I've installed xf86-video-ati i stopped sddm and xorg and i have executed X -configure then i copied the device section of the radeon (it has the PCI address) and adapted to the new xorg.conf file and now everything works fine.
But i've noticed something stranger i have downloaded again the iso and after the update i had no Xorg only terminal what i did was to reinstall nvidia and execute nvidia-xconfig.
Anyway the problem has been solved and now the second monitor works as it should.