First, in such cases please try to use one of the following:
Meta+T, Ctrl+Alt+T to hopefully pull up Konsole Terminal
-or-
Ctrl+Alt+F5 (Or F2,F3,F4,Fx…) to switch to TTY
-in either case-
Then you could perform systemctl reboot or systemctl poweroff to reboot or shutdown.
Also please see this and return system information: