Hello there, squidney31091.
When facing issues with updating iOS over-the-air, the following Knowledge Base article offers some best practices for updating your device:
Resolve issues with an over-the-air iOS update - Apple Support
If your device doesn't have enough space to download and install the update, you can use iTunes to update your device.
If you can't connect to iTunes, you can make room for the update by removing content on your device that you don't use. To remove content, tap Usage Settings in the Software Update screen. Learn how to see the space used by your apps and their content.
Additionally this article provides some insight into how iCloud storage and backup works:
iCloud: iCloud storage and backup overview
Thanks for reaching out to Apple Support Communities.
Cheer,
Pedro.