Yesterday I wanted to update my 16.04 Xubuntu. When I ran sudo apt update && sudo apt upgrade (system wasn't able to complete the upgrade process), the system froze and I had to restart by force.
But now I cannot even start the system anymore. After each reboot, only the grub terminal is shown. I also cannot access the grub menu by pressing ESC key (my system is UEFI).
Do you have any suggestion how to fix this?