Dropdown Menu

Hi Folks
I'm attempting to convert one of my website to a responsive design and although things are going well but slow I am having problems with my dropdown menu.

I have 34 items in my dropdown menu and as you can imagine this is fine on the smaller screens but a very long list on a PC.
I would like to display the dropdown list in 4 colums instead of one long list.

My page is on a test address if you want a look at

Although I have quite a good working of html, some things in css are proving a bit harder to figure out.