Sydney – Can the Header section be seperated from Slider in Front screen?

Can i configure the sticky header section (with Menu) to not overlap with the slider image on the front page? For example, the front page image should start under the header section. I need the header with say white background to be fixed at the top of the page. It should still be sticky so as it appears when i scroll down the page.

I could not understand which css file i shud edit with what code, since new to php.

Reference site : Cognizant.com where the logo / header section stay static seperate from the images below but is still sticky.