The “icons” you’re trying to use are Font Awesome icons. You need to provide the link to font awesome for the icons to appear.
Your media query is not place correctly. It should not be placed within a selector.
On a side note, don’t try and replicate the sample projects. They show just one way of completing the project. The instructions say your project should be “functionally similar” and “give it your own personal style”.
I suggest to change your header position to sticky, and section with the id pricing set the height to auto , if you set it to fix like (n)px , then you have to set the height for mobile or every single viewport to adjust the sizing.