2x2 min. videos : Fixing the sound and remove low frequencies

I think that the cable connecting the mic and the camera was not working correctly and there is consistent background noise. Ideally, removing it and higher the overall sound to 0Db. Thank you for your help.
Here are the files: https://drive.google.com/drive/folders/1Hj-czpCdqBr9AQy1oYJ90NWyk9Mzz3bj?usp=sharing