z-index?

Hey, I’m using your plugin with visual composer. Site looks perfect except for one small detail, when I scroll down/up everything tucks away nicely under the menu except for my two buttons – Contact us and Book now that scroll right over the top of the menu and look really ugly.
I’m a complete novice with anything other than changing fonts/colors via css so help would be appreciated.

https://wordpress.org/plugins/sticky-menu-or-anything-on-scroll/