My computer doesn't shutdown completely

[Ralf Mardorf]

Take a look at the log files were stopping services, unmounting or
anything else hung.

journalctl -r -b -1
                 ^^ change this number, until you found a boot that
                 didn't finish

-1 is for the last, not the current boot, IOW showing the last shutdown.
On my machine the order is a mess, since I sometimes use systemd-nspawn
to run installs in a container.

With the string command you could search the binary thingy using
commands such as grep, example, search for "foo":

strings /var/log/journal/*/system.journal | grep -i foo

Good luck, I never could solve an issue by using journalctl.