This is one of those confusing Google approaches to a problem. As I understand it, any picture that you take that sits in your camera folder will automatically be uploaded to Google Photos when it has a data or Wi-Fi connection. Of course, this is if you have Google Photos set as your backup location and not Samsung's default to OneDrive. Google Photos also collects all the photos you have in the designated photo folders on your phone, so if you are not careful, you will end up with the original you took and the one in the folder that you stored your picture in, which is a folder designated by your backup settings. So, if you delete a picture in Google Photos, it will also delete the photo in your phone folder to keep them in sync, but it will leave the other copy in your camera folder if it's still saved there. As an example, if you use WhatsApp and have not added WhatsApp to your backup setting, none of the pictures or videos will appear on Google Photos. It's very confusing, but I think that's about how it works.
Regards,D
