When scrolling down, header remains fixed, how to change that

So when a user scrolls down (whether on PC or mobile) the header part remains fixed on its position. I am talking about the part where logo, title, links and main menu is displayed on top.
How do I change it so when a user scrolls down, the header doesn’t remain fixed and it should move up like other elements on page. This is very annoying especially on mobile as header takes a very large portion on screen.