You’ve purposely set the width to a fixed 800px ? So of course the image will not be responsive.
Try using units that allow the image to be changed like ‘vw’ or ‘%’ etc.
First of all, review the previous lesson on how to make images responsive. You are missing something in your #Image selector.
Second, you need to make sure you are using closing tags for all your div and header tags. You are missing some right now which could be throwing off your layout.