Issues with media queries only in portrait mode, mobile

Hello there 🙂

My site does not ‘fit’ on the screen correctly, something is rendering a huge amount of extra space that can be scrolled into to the right of the content. My site title is also being moved from the header and doesn’t stay fixed in position. This is only apparent on mobile while viewing horizontally. I’ve been looking everywhere for a fix but no luck as of yet. Any suggestions are appreciated.

The page I need help with: [log in to see the link]