To resolve the black screen issue you're experiencing with the Boxbollen app, please follow these steps:

1. Restart Your Device
Begin by restarting your iPhone. This simple action can often resolve temporary glitches affecting apps.

2. Check for App Updates
Make sure that you are using the latest version of the Boxbollen app. To do this, navigate to the App Store, tap on your profile in the top right corner, and scroll down to see if there are any pending updates for Boxbollen. If there are, update the app.

3. Reinstall the App
If the problem persists, uninstall the Boxbollen app and then reinstall it.
- Tap and hold the Boxbollen app icon on your home screen until it wiggles.
- Tap the 'x' to delete the app.
- Open the App Store, search for Boxbollen, and reinstall it.

4. Check Permissions
Ensure the app has the necessary permissions to function correctly. Go to Settings > Boxbollen and check the permissions, especially for location, notifications, and microphone.

5. Connection Issues
The app may require a stable internet connection to operate properly. Ensure you are connected to Wi-Fi or a cellular network. You can check your connection in Settings > Wi-Fi or Settings > Cellular.

6. Clear Cache
While iOS doesn't allow you to clear cache like Android, closing background apps can help. Swipe up from the bottom of the screen and slide the apps off the screen to close them.

7. Contact Support
If none of these steps resolve the issue, consider reaching out for technical support via the official Boxbollen website or through the app’s help section. They may have additional solutions or be able to provide updates on app issues.

If you find that the app continues to show a black screen, consulta online communities or related forums, such as discussions on Reddit which might provide additional troubleshooting tips or similar experiences – learn more - learn more - learn more.

By following these steps, you should be able to resolve the black screen issue with the Boxbollen app effectively.