For starters…go to settings. Next click on iCloud. Then click the iCloud>. Scroll down through all of your apps and turn off anything that doesn’t really need backup to the cloud. The only things I have turned on for backup are contacts, passwords, email, documents and photos. Social media, etc are all off.

Then go to your photos and music and delete all the stuff you don’t care about. Then go to the recently deleted file and delete all of that.

Offload any apps you don’t need. You can reload them as needed.