Hi there!
Thanks for your query.
The navigation is sticky but it is hidden under the header as the header is also sticky. So you can set the top as auto or inherit to get it below the header.
Here is sample code, you need to put in your custom CSS:
#sp-page-builder .page-content .sppb-section.sppb-sticky-it, #sp-page-builder .sppb-section.sppb-sticky-it{
top: auto;
}
Hope this will solve the issue for you.
Note: Path towards custom CSS:
Extensions>Templates>Styles>
Click on your current default template name then choose Template Options.
Then find custom CSS within the custom code.
https://prnt.sc/pu705g
https://prnt.sc/pu70zn
Best Regards