There is one possibility: if you deleted the track on the web from your PC and didn’t have the app running on your mobile at that time (so synchronization didn’t occur), then the tracks may still be on your mobile — if they were there after the last (previous) sync.
If that’s the case, first disable mobile data and Wi-Fi on your phone (or enable airplane mode), and only then launch the Mapy.com app. This way, synchronization won’t happen, and the app will still have the local data.
You can then export individual tracks or entire folders to GPX files.
The exported files will then remain stored in your phone's memory — these are separate files and not part of your account, so nothing will delete them automatically.
If you're able to export the tracks successfully, you can then turn your data connection back on and allow the app to sync. The tracks will be removed from the mobile app as well — there's no way around that.
If you deleted the tracks from your mobile device, it's likely that you were connected to Wi-Fi or mobile data, so the deletion was immediately synchronized. In that case, the data is no longer available even in your web account.
If you manage to create GPX files, you can then import them back into your account. If they are recorded tracks, make sure to select “Activity” in the import settings (pencil icon) during the import process.
