Grid-a-licious theme help

Hey all, not sure which forum to post this in so apologies if it’s the wrong one.

I am using template Grid-a-licious for my website Thinking Hats — Creative Thinking and I’m wondering two things;
– If I can make the top navigation deeper? When I try it goes behind the image boxes?
– Also if I can make the navigation float, so when the page position has changed/scrolled, the navigation bar will always remain at the top? How would I go about this?

I guess my main concern is how to make the top area (logo and navigation) deeper. I wouldn’t mind trying to line up the logo and menus on their baseline.

Thank you in advance for any help or references!