Floating Navigation for Grid-a-licious

Hey all

I am using template Grid-a-licious for my website https://www.thinkinghats.net.au/thinkinghats 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?

Thank you in advance for any help or references!

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