how to remove mic repeating what is hear in the conversation away

This is usually to do someone having their speaker volume set too high which gets fed back into microphone. It can also happen if more than one person is in the same room and in the same voice/video chat. You can use headphones which should eliminate this, or you can lower the speaker volume and lower the microphone's sensitivity so it takes a louder sound to activate the microphone. You can do this through the app or through the Sound System Preferences. Of course, the problem may not be with you, but one of the other participants.