The app runs entirely locally, on your iOS device. It does not need a network connection.
The app does not collect any data, period.
The user can access any file locally accessible on the system.
During the TestFlight phase, if the application crashes, a crash report can be sent to the developers. This crash report will contain information about what caused the crash (functions being called, values of variables).
The owner of the application, [Hans Schülein](mailto:firstname.lastname@example.org, does not have any way to access the data viewed or created by the user.