Thanks Andy - and others who have replied - I hadn't thought of emptying Trash, and it's a good suggestion. I had 700 emails in there this morning. Every once in a while, I do want to go back to an email which is in Trash, but of course there's no reason to keep 700 bits of communication in there.
By the way, I keep enough Archived emails, and enough photos, that I went ahead and bought more storage. I'll also look into backing up to Google Photos, if I can do that without Google compressing them ( sometimes I want to print, or display at a large screen size).