Banner Image Won't Resize for Mobile View

Site URL: https://www.oxenfart.com

Hello, 

Our banner artwork appears fine on our site when viewing on a computer screen, but the mobile view does not resize the banner and cuts off the bulk the image versus resizing for the mobil platform. Any tips on why this is happening, and how resolve it? We've found that the majority of site visitors use mobile, and don't want to reduce the impact of the image.

I already used a CSS Code but when the image resizes there is a large space underneath the image.

Thanks in advance.

Add to Design > Custom CSS

@media screen and (max-width:640px) {
body.homepage .Parallax-item:first-child img {
    width: 100% !important;
    height: auto !important;
    top: 0 !important;
    left: 0 !important;
}
section#home-team {
    min-height: unset !important;
    height: 200px;
}
}

Thank you so much @tuanphan. It worked right away. 
Now it looks great!

Best regards, Benjamin