Thanks for asking.
I checked the website and can confirm that mobile menu is not working. Reason why mobile menu might not be working is because you are using incompatible version of X Theme and Cornerstone. As of now I see that you are using X Theme 6.0.4 and Cornerstone 3.1.6 which are incompatible. Please update X Theme to the most recent version 6.1.6 and see how it goes.
Before doing so, it's advisable to take a complete backup and test the update on a staging server. I am sharing few resources that you can refer:
Version compatibility guide: To learn about the latest and compatible versions of bundled and supported plugins, please take a look at following doc:
2. Theme Update guide: Please take a look at following article to update Cornerstone.
3. Please take a look at following doc about changelog:
Google Analytics: Please make sure that you are using latest version of Google Analytics plugin. Now you just need to enter Google Analytics Id to integrate Google Analytics. Here is a tutorial that you can take a look.