Adding a "slide up" navigation bar/header to the Thomas template in Portfolio

Hello,

Please can someone help me to reproduce the sliding navigation bar from the Thomas template in Portfolio, as can be seen in the example from Sever Acar

https://portfolio.adobe.com/examples/

On the landing page the menu/navigation bar is on the footer of the page, but when the arrow is clicked the navigation bar moves to the header of the page and the background image is replaced with a gallery.

I can't find the option to replicate this. I am using the Thomas template.

Many thanks

T