Let's go over the steps you need to take
to delete photos from your iPhone but not iCloud.
Open your settings app.
Then press your Apple ID.
Then press "iCloud."
Press "Photos."
Then, next to "iCloud Photos,"
press the toggle to disable photo sharing.
If you have optimize iPhone storage enabled,
you'll have to choose "Remove from iPhone"
or "Download Photos & Videos."
Either option will keep originals
saved within your iCloud.
Let's set up a different iCloud server
for photo backup.
For this example, I'm going to use Google photos,
but there are many other cloud options
you can choose from,
including OneDrive, Dropbox, or Flickr.
Open the app store app on your iPhone
and download Google photos.
Open the Google photos app.
Press "Allow access to all photos."
Then grant access to your photos
by pressing "Allow Access to All Photos."
Choose if you want Google photos
to send you notifications.
Now choose what Google account you want
to back up to.
Now choose your backup options:
storage saver or original quality.
If you don't want to lose
the highest possible quality of your photos,
then choose original quality.
If storage space is a priority,
then choose storage saver.
This setting will slightly reduce
the quality of your images.
The backup process will automatically begin
and can be monitored
by pressing on your profile image.