Yes, simply start your video call on MeetFox, press the screen-sharing icon, and your customer can see your screen. Also, your client can share their screen with you at any time.
If you are the newest version of MacOS, you will need to give your MacBook the permission to access screen sharing (a new update, Apple has introduced). Please go to "Privacy" within your "System Preferences" and click on "Screen Recording". Please allow access to your browser by checking the respective checkbox.