[Theme: Skt-photo-session] Problems with background image

Hi guys. I’m developing my first website using WordPress with the skt-photo-session theme. This theme is supposed to be responsive, but I have a couple of errors while navigating the web via smartphone/tablet. The tabs of the menu are bigger than spected(smartphone) and the background photo in ‘Inicio’ is cropped (zoomed-in)(both). These two errors don’t show up while navigating the web on PC. You can check the web at qubik-design.co.nf

Thanks in advance.