Perhaps you tried out Google Photos and decided it wasn’t the right backup solution for you. Just uninstalling the app alone, however, won’t stop your pictures from being backed up to Google’s servers. That’s because photo backup and other key settings live in the Google Settings app on your Android device.
To stop photo backup or adjust other backup options, look for Google Settings in your app drawer. Select Google Photos Backup and flip the switch to Off.
Once you've done that, take a minute to see what more Google Settings can do, as it controls many aspects of the apps that save your information to your Google account. Other useful tweaks include choosing to upload images in their original size or a compressed format, which folders to save, or whether to use mobile data for backup.