storage full

Free up storage space on your Mac - Apple Support

If you are using iCloud Photos,

• Deleting photos from your Mac will cause their deletion from iCloud, and from all other devices connected to iCloud Photos for that iCloud account. You'll lose those photos (unless you've already manually saved copies elsewhere – outside of Photos).
• You can go into Photos Preferences and select "Optimize Mac Storage". (This is for the old version of Photos that I'm using; your Preferences dialog may look slightly different.) This gives the Mac permission to toss out full-size local copies of photos, as needed, on the basis that it can re-download full-size photos from iCloud, later. Unlike deleting photos from your Mac (which will be taken as a request to delete them everywhere), the use of "Optimize Mac Storage" will not result in the deletion of your photos from iCloud.

If you have a lot of videos and photos in Messages or Mail that could be taking a lot of space if they are downloaded to the machine. I would delete old messages and emails that you might not need anymore.