Are you sure they are duplicate pictures or are you seeing the "recents" album in galaxy and assuming the pictures there are duplicates? The recents album is only a virtual album and will show your most recently added or accessed photos for easy locating. If you delete photos from that "album", you will also be deleting them from whatever album you moved them to. In other words, deleting them from the phone. If you are talking about your backups synced with One Drive or Google Photos, deleting any picture from the cloud drives will delete it from your phone. Deleting photos from your phone will keep them saved in the backup cloud location.
So, make sure the duplicates you want to delete are actually duplicates and not just virtual duplicates. Otherwise, the app you use to delete duplicates would be the Gallery app. Just set the tab to "pictures" which will show you all your pictures by date and just long press any photo to make multiple selections and hit the delete icon to delete, or just tap an individual photo and hit the trash can icon to delete.
If you are talking about finding duplicates and eliminating them, go into file manager, scroll down and tap "manage storage" and then scroll down for duplicate files, and it should come up with a list of any files that have the same name and you can choose to delete any/all duplicates. This will show you all duplicate files, not just photos.
