Moving Fees to External drive

Why don't you move your photos to an external drive? You could do the entire photo library giving you lots more space. FYI, you need to maintain an absolute minimum of at least 15 - 20 GB of empty space at all times in order to allow the computer and OS to function properly (more is better, especially on an SSD). If you fill it up completely, your computer will simply stop functioning.

If you want to do that, I would put them on a separate drive or on their own partition. Otherwise Time Machine may delete them when the drive gets too full.

If you are talking about Photos.app photos, it is not recommended to store Photos.app libraries on Time Machine drives (it might corrupt the library). Get another drive and format it as APFS (SSD) or Mac OS Extended HDD and Finder > Get Info > Ignore ownership on this volume. Remember to backup that disk to another disk, if you do not want to lose the files.

The OP will need to add another external drive to backup that photo library external if you are recommending that he not backup with TM. Since he is trying to move files off his internal, there would be no backup for them unless you add another.

FWIW, I did not recommend storing the photo library on a TM drive.

Start with the largest in file size.