Help making background image responsive
I'm trying to make my main image responsive on https://www.corporateebooks.com/
Currently, in mobile view it just reverts to a gray background, so it's a pretty bad experience (likewise with a lot of the mobile site). So I could probably do with some major changes overall.
I started with a template from the Marketplace, and have just been learning as I create the site, so I'm pretty novice. I'm sure it's a simple fix, but I'm having a problem figuring out where to change the code. Any suggestions?