Child Theme not behaving

There are two problems with this page; The green portion of the header isn’t scrolling and the content has floated to the top and appears beneath the header.

My goal is to use a child theme to create a fixed header, so that my logo and navigation stay put on top and everything from the green background on down, scrolls continuously. I’ve already activated the child theme and copied the desired css from the main style sheet to the child theme style sheet.