The files are downloaded with the tablet's file manager.
In the app you choose the folder that contains the music files.
The Do it result is: The operation is list empty? cannot accept the arguments:,[pp]
I don't understand Danish, if you are looking for help here you should use English as the language and (temporarily) set the language in the designer accordingly.
What I've noticed after a quick look is that you're using fairly old extensions (versions). As far as possible, you should update these extensions. That would at least be possible for @Taifun's TaifunFile extension (Feb 13th, 2021: Version 13a).
I really apprecite that you try to help me. I am totally lost.I translated the app to english.
The music is from the start placed in the internal Music folder.
After you find your music, it should be possible to play it when clicking "Listen".
It works in android 5.0 and 7.0, but not in Android 10.5
Why not make life easy for yourself and create a simple test project that handles file locations and playback. Once you get that working you can apply this to your main project.....