My launcher is launching but nothing appears, just a black screen

Hello,

Since i bought my computer at a friend's and let minecraft open, i can't re-open minecraft. It seems like minecraft don't like when we change the connection and let it open.

the launcher is launching, but nothing happens : there's just the black screen of the window.

i tried everything : uninstall it and do it again with/within the antivirus on deleted all the files ...

please help me !