Regretfully, we do not have support for third party plugins and custom code. Please consult with a third party developer for this.
I checked the site you posted and it functions like a one page navigation which is a feature offered in our theme. Specifically, it includes:
- Smooth scrolling to section (all links in X are smooth scrolled)
- Sticky header offset
- If using the X or the Classic Header, the One Page Navigation offers the ability to choose or set a specific menu for a page.
Please see https://theme.co/apex/forum/t/features-how-to-setup-one-page-navigation/96.
Please just note that we can't replicate the other functions of the site you've posted.
Thank you for understanding.