People seem to have a love / hate relationship with the new APFS file system in the macOS. I like it, but others have had problems with the way it does things. The APFS file system is the future of the Mac, Apple is improving it all the time. However, if you have gone to the APFS file system and are having problems, you may wish to revert the hard drive in question to the old HFS+ file system. This article explains how to do that. It is quite detailed, but it looks doable. Obviously, a good backup is in order before proceeding.