Jquery menu drop-down hiding behind other elements

I’m relatively new to WordPress (I’ve been using it under a year), and I’m having some trouble that I can’t seem to fix in any way that seems “logical.”

I’m using a theme called Radion (doesn’t have any support). I’m doing this for a client who wanted a lot of custom changes to the theme, which I’m guessing is where my problem stems.

The problem is that in the “mobile” version, the drop-down menu hides behind the rest of the items. I’ve tried changing the z-index of every item I can imagine, but I feel like it must have something to do with the JS instead (I am not very familiar with JS).

Here is the site:

http://www.hilerlawoffice.com/

Please let me know what pieces of code you might need to fix this. I am totally baffled, so I’m not even sure which parts I should include on here.

Thanks!