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 using the latest version of macOS, you may need to update your privacy settings to allow screen sharing. To do this, go to "System Preferences", then "Security & Privacy", then "Screen Recording". Make sure your preferred browser is check-marked to allow screen sharing.