Now, since you can get to grub>
Do this (get to grub prompt) and type in the following
grub> linux /boot/vmlinuz-x86_64 driver=free lang=en_US keytable=us tz=Europe/Rome
grub> initrd /boot/initramfs-x86_64.img
notes: I assume you’re in Rome, but you can change to whatever you’re in. If unsure, don’t worry about it. Just use Rome and we can fix it after installation.
ps: not answering your Q right now. Just proceed. If done, we’ll talk later.
Also, very late, as usual, for me here. Good night.
Oh… then you have a grub from somewhere.
See this if it can help.