Can't open PMS after trying to restore the database

When trying to restore my database using Plex instruction “Restore a Database Backed Up via 'Scheduled Tasks”
I will not get in contact with PMS after my changes. If I had made mistakes during the process is it anything but reinstall Plex that I can do?

There are some questions to the instruction “Restore a Database…”
It says ”You don’t want the ”shm” and ”wal” files to remain in that directory”. Does this mean that all files with those endings should be removed or just those two mentioned.
Which backup file shall I choose, the latest? It says that I should dublicate the file and rename it. Should I keep the original file in the directory?