How to display your image in the Wordpress menu when scrolling?

Question

PHP

Hi guys. Please help and thank you in advance.
There is a need to display your picture in the main menu, in an empty place, when scrolling down the page.
Relatively speaking, any PNG image, not the site logo.
Link to the site lornabyrne.grantdevelop.com
There is an empty area, highlighted it in red snap.ashampoo.com/sGt5uUxr
When I scroll down the page, the area is still empty snap.ashampoo.com/U4MWj2Jm
?
Maybe a function of some kind or a call to something that I have no idea about?
Here is the php code from the theme header. Maybe this will help somehow: https://codeshare.io/aNrzQ
Any help is appreciated.
Thank you!