Cannot empty trash and deleted files in iCloud keep returning

Have you tried these things?

• Force empty the trash with option Finder>empty trash
• Restart the computer (of course)
• Re-start in Safe Mode. This bypasses certain potentially disruptive processes, and it often helps. Safe Mode is different for different computers, so see this: 

          Start up your Mac in safe mode - Apple Support 

• Use Terminal (in Applications>Utilities) and type

sudo rm -R

with a space after the R. Then drag files from the Trash to this line and hit Return. It will ask for an administrator password. I'm no expert at this Terminal thing-- I just type what I read. It works for me.

Having full iCloud storage makes it hard to delete stuff. I'd probably pay the extra three bucks or whatever for one month of extra storage, and see if that works.