A useful command sequence to know and remember is to depress the keys
Command, Option, and Escape simultaneously. This brings up the Force Quit (process) that is reached via the Activity Monitor above and has the advantage of being less complex and much faster.
I have used it many times to kill MS Excel, Safari and other programs that go off track and give me the spinning beach ball until I kill them. You may test it at any time and then close it via the left corner X if you decide not to use it. Normally after I kill a process, I restart the computer to clear most of memory as well.