I believe you just open the mapp and drag it out to another location, another mapp ! Hemlig mapp is pass word protected created by yourself! Or separat pin kod, i am not sure about that. It is a suggestion only, if it works i don't know?
It seems it is a system mapp and it can't be deleted. I went to setting and create a pin kod, whit that I activate hemlig mapp. In it created foto, Samsung internet, files, kontakter, kalender. And those is not able to delete, but files saved in those apps can be deleted. In case I might be wrong hopefully someone else will be give correct answer to your questions.
Open the app go to location of file and mark it and press 3 dots and pick move out from secure folder/hemlig mapp. That way it will transfer data you selected out from it. But app itself cannot be deleted since it's part of Samsung official ROM.