ehhh not sure that you can. I had to move all of my pics out of gallery when I wanted to remove Google pics. Google deleted their version and synced with my now empty Samsung Gallery. once I removed Google pics and disabled the account I added the photos back into gallery...a bit of a pain...followed this here https://www.guidingtech.com/delete-photos-google-photos/
just be careful though with your photos. I no longer use Google photos as have all my files and photos in OneDrive. you need to be clear if you are just trying to make space in Google or you no longer want to use it. this will drive what you do with your photos.