To backup your photos, you need to use the Google Photos App. To set up automatic photos and video backup, launch the Google Photos App and follow these instructions:
- At the top left, tap Menu
- Select Settings > Back up & sync.
- Switch on
If you see a message asking to allow the app to access your photos:
- Open the iOS settings app > tap Privacy > Photos.
- Switch Google Photos on.
You can read more about the Photos Backup and Sync here:
https://support.google.com/photos/answer/6193313?co=GENIE.Platform%3DiOS&hl=en
You will not be able to save iMovies that are in progress. You must export the iMovie as a finished project to the Camera Roll for it to be backed up to Google Photos.
After Google Photos is setup, while connected to a WiFi network, launch Google Photos and it will automatically backup any new photos. This is a good way to always make sure your photos are automatically backed up. Remember to launch Google Photos on a regular basis.
The process of setting up Google Photos is illustrated below: