Open the Google Photos app or go to photos.google.com
Tap or click your profile picture in the top right
Select the Google account you want to remove
On Android, go to Settings > Accounts or Device settings
Tap the Google account
Select Remove account
Confirm the removal
On iPhone or iPad, remove the account from the Google Photos app by signing out or removing the Google account from the device settings
If you only want to stop using Google Photos, turn off Backup and sync in Google Photos settings
If needed, delete the Google Photos app from your device after removing the account