Due to major issues after Catalina upgrade I would like to restore my Macbook from a Time Machine Backup

I've been unable to use Microsoft Office after upgrading to Catalina in Nov 2019 therefore would like to restore my 2015 Macbook Pro from a Time Machine backup (external hard drive) and revert to an older OS.

When I try to do this in Recovery mode I get the following error message - can someone please help I have no idea what HSF systems or APFS volumes are.

"The system can't be restored onto this disk because HFS systems can't be restored to space sharing APFS volumes. Reinstall macOS on this disk and then use Migration Assistant to transfer data from your backup instead."