Decrease navigation bar thickness on mobile + increase logo quality

Hello, I have just purchased the pro version of radiate. I am looking for a way to decrease the thickness of the navigation bar.

I have added css so that the nav is sticky on mobile.

I do not use a banner, I only have the featured section at the top of my page and the nav bar is overlapping with the featured section on mobile. Is there also a way to add some background space above the featured image that isn’t a banner?

Finally my logo is blurry & when I increase the pixels it makes it too big, is there a way to compress this so it is better quality & the right size.

I appreciate any help, thanks

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