>Is it somehow possible to automatically store these backpack files in a specific directory on mobile.
so that another app (developed by our team) can read these files
I don't think this would be possible. Apps on Android and iOS are containerised. One app can not access another apps files, or even a file outside of its own container.
For Android you could create your own custom APK with the files, and push that though. And when you update the files, just push the APK again.