Remove Navigation Menu from header

Hello, so far I managed to do the inserts I like for my page, but I’m stuck with this.
I’d like to remove both the Navigation menu and the black background showed on top of all pages, I like the one displayed when scrolling down, not the one that is always on top. I tried some custom CSS codes from other topics, but none has worked for me so far. Any help?

This is the site itself: http://www.ukulelesprout.com/

Thanks, I’ll really appreciate any orientation I could get