Photos and videos in the Recycle Bin of the Gallery app are automatically deleted after 15 days (30 days on Android 10/One UI 2). You can empty the Recycle Bin as well as delete individual files in it. If the photos are deleted from the Recycle Bin, they can no longer be restored.

Android 10 (One UI 2.0)
Step 1:  Open the  Gallery -App
Step 2:  Open the  menu
Step 3:  Tap on  Recycle bin
Step 4:  Tap on  Empty
Step 5:  Confirm with  Empty Recycle bin
  1. Open the Gallery-App
  2. Open the menu
  3. Tap on Recycle bin
  4. Tap on Empty
  5. Confirm with Empty Recycle bin

Samsung Instructions