Margin-left doesn't change with media query

Hello,
In the media query I aske to position nav bar at the bottom and remove the margin-lef of the main section.
The media query make the job for the nav bar but not for the margin-left.
https://codepen.io/ALL9000/pen/yLzQKmv
What’s wrong. ?

Looks like you’ve figured it out. Good job!

Yes Thank you for the compliment.