hi
You ...... post the output of this command:
i wrote itin terminal but nothing happens

You .....----------------------------------------------------
How did 4.0 get installed with Grub? Where did Grub come from, how did Grub install an ISO, who/what created the Grub menu, and why doesn't the grub menu display when you turn the pc on? When you get a chance please post the output of this command:
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ok another time (lol)
so i have installed P 5.01 and it was problematic with (black screen ) after days with this prob i decided to install P 4
i installet it in USB and opened it fresh mode there i choise option (Porteus Installer) i prepared the partition sda3 EXT4 end started option installer and ask me to write (ok) end after 1 min ask to clik enter at this time is open a litel interface install Porteus in sda3 partition end ask me if you want to install the grub i choise ok end enter 1 mint later Porteus is installed --- you can reboot now