Header Image not Responsive for Iphone

Good morning, I purchased the Photofocus Pro yesterday and started to build my page. So far I am making some progress. The only thing I cannot find a solution for at the moment is the header image. It’s not responsive for mobile devices and far too big when I check the page on my iphone. The Url is http://opgenoorth-art.com/ Thank you for your support, Jna