Here's how to backup from Google Photos:
- Open your web browser on your computer and go to https://photos.google.com/
- Sign-in using your email address.
- Select everything you wish to download (checkmark, top left of photos).
- Click the ellipsis (3 dots) on the right side of the page.
- Select "Download".
- This will download a zipped file containing your selected photos. Unzip this folder.
- Then use the desktop app to backup all those photos.