Please try the below:
1. When an app isn't responding, close the app and go to Settings > Apps > See all apps > Find apps > Storage & cache > Clear storage and Clear cache, and try again (ensure you back up your data before clearing).
2. Too many background apps and processes can lead to insufficient RAM, which slows system programs down. Close and clear unnecessary background apps.
3. If the phone is running for a long time and the CPU is overloaded. Restart your phone and try again.
4. If developer options are enabled and your phone displays 'Application not responding' (ANR), we recommend that you turn developer options off.