Hi Greg,
Thanks for posting your question regarding the Menu appearing behind the content (Call to Action) on mobile devices. I was able to replicate and see that this is only happening on iOS devices.
I recommend removing the custom CSS that you have added as it seems to have disrupted the responsiveness of the theme. If you are interested in customizing a BoldGrid theme, I recommend installing a Child Theme and develop your customizations using that theme.
For more information on using the BoldGrid Theme Framework for developing your own theme(s), you can review our documentation.
Best Regards,
Carlos D