To change how long downloaded files should be kept:
1. Go to settings (icon in the top-right corner).
2. Select the Files tab.
3. Press the "Keep downloaded files" option.
4. Here, you can change how long downloaded files should be stored on your mobile device.
5. You can cancel the operation without any changes by pressing the "Cancel" button.
Depending on your selection, files that are older will automatically be deleted, unless they are marked to be available offline.
Files marked as available offline are never removed.