Move the Main Navigation under the first section

Hi first I want to thank you for all the help and response and answer to all my questions…

I have a two part question…
1) Is it possible to move the navigation from the top tagline and place it under the image and as the page scroll it stick to the top….and with that keeping the logo at the top in the top tagline and as the page scroll it stick with the logo…

for an example look at this site: https://www.atidydesign.com/

Before I mess with changing CSS or Html is it possible and do I have to work with customizing CSS?

2)Where would I go to make changes to the font-text or do I have to locate area in CSS and make the customize changes there?

Thanks much if I can accomplish the first question that would solve a huge challenge….