Low storage problem

Nothing short of magic. There's no way to make room, without deleting something. There's no magic way to get more room on an iPhone.

If you are low on storage, you need to delete content, or move it off the iPhone.

iCloud Drive is Apple's online storage option for Backups and synced content like Photos and Files. You cannot delete it. You can turn it off, but that would stop the connection to the computer if you use things like iCloud Photos, or contact, Notes etc...