how to make content scroll below sticky navbar?

I’m using the Florentine theme, which does not have a built-in sticky menu. However, I found a plug-in (Sticky Menu (or Anything!) on Scroll) which has worked to make my .navbar stick to the top of the page after the initial scroll.

My problem is that the content of the pages scrolls up and under the menu making the texts of the content and menu overlap and become messy and unreadable. I would like to make the content scroll off the page before reaching the menu. The menu is just text over top of the site’s background image, which I like, but am willing to add a background specifically to the menu if needed (I just don’t know how to do any of that).

I am also happy to stop using the sticky plug-in if someone can provide me with the right way to edit the css or js to get the overall effect I’m looking for (menu scroll up to top and stay there, content scroll up and disappear behind menu so that menu is still easily visible).

I’m not sure if there’s a specific way I’m supposed to share my site for people to look at the code, but here’s where I’m working on it:
http://dandelionlearning.com/bg_dandelionlearning.com/