Hi @Mapi09 Deleted Images should be accessible for 30 days , check if this is toggled on in the Gallery Settings. Have you checked My Files, Image and Videos to see if the files can be accessed from there? Do you have any Backups set, I would suggest that this is strongly advisable. If you have a cloud Back Up in the Gallery Settings you can sync with One Drive. if you had backed up to Google the files may be avaiable there.
You can also swipe from the top to the bottom of the screen twice to access the all the quick Panel Settings and tap sync if it is not switched on. See more about the panel here https://www.samsung.com/uk/support/mobile-devices/quick-settings/
If all else fails you could try Android Recovery software , some examples here https://www.makeuseof.com/recover-deleted-files-android/
@jpvdvyver: Have you tried the steps above provided by @JAMES4578, especially checking My Files > Images, and Google Photos/Google Drive? I'd also recommend heading to the Galaxy Store > Tap the 3 lines in the top left > Updates, to see if there are any updates available for the Gallery app that might address the issue.