What ' s the first action you should try when an app is unresponsive?

The first action you should try when an app is unresponsive is to force the app to quit and reopen it. This can help resolve temporary issues that may cause the app to freeze, crash, or not respond to your inputs. To force the app to quit, swipe up from the bottom of the device. If your device has a home button, double press that instead. This will bring up a carousel of all the open windows on your device. Swipe left or right to find the app that you want to quit. Swipe up on the app’s preview to close it. Then, tap the app icon on the Home screen to reopen it and see if it works as expected.  References :  If an app on your iPhone or iPad stops responding … - Apple Support