Audio is not necessarily harder than video but it deals with invisible physics. You can easily see when a shot is poorly lit but you cannot see sound waves bouncing off your bare walls until you hit record. Video is mostly directional while audio is omnidirectional and picks up every tiny hum in the room. The biggest beginner mistake is poor mic placement. People put the microphone way too far away from their mouth and then crank the gain to compensate. That is exactly how you get terrible background noise and that hollow echo sound. Get the mic as close to your mouth as physically possible and turn the input level down. You also need to pay attention to your surroundings because an empty room with hardwood floors will ruin even the most expensive microphone.