What do I do if an application is not responding?
Make sure the application is open and press Alt + F4, which will shut down the application.
If this doesn't work, open Task Manager (shortcut: CTRL + SHIFT + ESC, also see: How do I access Task Manager?) and right-click the task which is not responding. Click end task to shut down the application.
Restart the application after giving it some time to fully shut down.