Divi – Nav sticky.. but floating mid screen

Help! Sticky nav is floating mid screen ??
Using Divi framework.
I would like to crate a nav like this: https://laffinage.co.uk
Where the 3rd row is sticky on scroll.
I’ve followed the ET Tutorial: https://www.elegantthemes.com/blog/divi-resources/how-to-make-any-divi-page-element-sticky

The 3rd light green row is just floating mid screen on scroll. I’d like it to move and stick to the top on scroll (see example site).
Any advise would be great! Thanks

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