A. Try closing the app completely and restarting it. On Android, you can do this by going to 'Settings' > 'Apps' > 'ID Photo Phd-passport photo' > 'Force Stop'. Then reopen the app.
B. Ensure that your device has enough storage space and memory available. Clear cache by going to 'Settings' > 'Storage' > 'Cached data' and clear it. This can help improve app performance.