Header not responsive

Hey,

Kind of a huge problem on my website using the oblique theme.
When on a computer, no problem the website is just perfect.
However, whenever i’m on a tablet or a phone, the site’s header just goes insanely huge, and it’s kind of ugly. Don’t know if I messed up in some setting, been doing some researchs but can’t seem to find a solution.
The website : http://hophophop.eu

Thanks !

The page I need help with: [log in to see the link]