Pick some apps and see if you can select the “Move to SD Card” option. Not all apps have this selection, but many will, and you can free some space.Or delete some pictures or videos.

Turn on your camera.Press the “Menu” Button.Go to the “Recycle Bin”, then select “Recycle Folder”.Recover photos from it.

If this way doesn't work,try Samsung data recovery.

Hi Mariah. Try this app I found on Google Play store: Photo Recovery (link)