Hi
I am using Leap 42.2 . When I shudown the computer it takes several minutes. First I right-click press leave then I press the shutdown button wait for about 40 seconds the screen goes black then the screen reappears again for another 40 seconds, then it goes to runlevel 3 after that it shuts down .
I am not sure what information I can provide to help
Thank you
42.2 is, as I’m sure you know, very much end of life 
Perhaps consider updating?
The following may help in your efforts to debug the slow shutdown…
https://freedesktop.org/wiki/Software/systemd/Debugging/#index2h1
Check /var/log/ for bloated files. Logrotate might not be running automatically. On an older installation, some log files can become massive, and take a long time to update activity. If I’m right, do
logrotate -f /etc/logrotate.conf