how to delete duplicate photos, and organize my library

This document should help with deleting duplicates;

Find and delete duplicate photos and videos on iPhone – Apple Support (AU) - iPhone

Remove duplicate photos in Photos on Mac – Apple Support (AU) - Macintosh

Photos in albums are not necessarily duplicates. You can add a photo to many albums, without creating a copy of the photo. Each photo will only be stored once in your Photos Library and the albums are referencing this one instance of the photo. You will only get a duplicate in your library, if you import the same photo twice and ignore the warning about a potential duplicate. A photo is only a duplicate, if you are seeing it twice in the All Photos album.

If you upgrade your mac to macOS 13 Ventura, you can use the built-in duplicate detection to find duplicates, as shown in the links in the previous post. But this requires macOS 13.