Is there any way I could access the files of the device that is using that app and have the ability to modifyfiles
Maybe this will help you ?
What kind of files are you talking about?
Media files or non media files?
See also Some basics on Android storage system
Taifun
Media files and maybe other types if possible
You could use the FilePicker and File component if you just want to modify and retrieve files, File component can delete, modify, and Create files And Directories.
File picker will let your user select a file.
@TIMAI2 is an expert on that.
_Junko