#Android has always lacked a way of getting rid of sounds in your phone quickly unless you own a OnePlus, so now in Android 9.0 you can set up a shortcut in sound settings by which you can press the lock button and volume button together to instantly silent your phone. Comes in handy a lot for folks who have many meetings.
Settings>Sound>Shortcut To Prevent Ringing>Press Power & Volume Up together>Choose Mute/Vibrate/Do nothing.