How to assign different menu element to a single page

I created a landing page and tried to assign a separate menu to it:
https://www.bocaratontribune.com/beauty-and-wellness-expo/

However, when I change the header to this page, the whole site changes from the default menu to the dedicated menu for this page. I am not sure if it has to be fixed using the Website Manager or if I am using the wrong element.

I also tried to apply the specific menu creating a raw instead of a header box but then the mobile shows the menu items horizontally instead of a hamburger.

Any help will be much appreciated.