Custom CSS messing with mobile version of site

Hello, I was talking with someone in the support chat and they suggested I open a ticket here. I have a site, http://www.prideflight2018.com that looks poor on mobile devices. I believe it is because I am adding additional styles using the "Additional CSS" portion of the visual editor. However, I cannot figure out the root cause of why the mobile site looks skewed. I tried to use media queries to overwrite the themes inherent CSS stylesheet but it didnt work out for me. I will grant access to the site if needed.

Thank you! Have a pleasant day.