The CSS is processed in chronological order so having a setting at Line 1 will be overridden (generally) by a change to that same property in Line 10.
So my point was to add the @media statements after the 'normal' code in your CustomCSS panel or child theme style.css.
Can we have a link to your site to see what is wrong?
(When posting, I can see you've tried to use / for your code. If you look in the panel where you write the post, there are some buttons at the top, including [code].
When you press it once it adds a backtick and the button changes to [/code]. Then enter your code. Press it again at the end of the code for the 2nd backtick. This is how you get the code shading in posts)