Boundless theme navigation bar

[MVUILL]

Hello ! 

I use the Boundless theme, I would like the sticky navigation bar to display the subcategory when clicking on a category (either for a collection of product or for informative category). In the theme page presentation by shopify it works like it and I want it exactly like it! 🙂 

I created a dedicated menu (called menu sticky) and a menu for each category as I've seen on some posts but it's not working: when clicking on the category, nothing happens. 

Any idea ? 

My website is www.french-address.shopify.com pswd: bewvep

Thanks a lot!!