How to make a responsive full screen video in the header of the site?

Question

css

You need to embed the video on the main page so that when you start it appears immediately in full screen mode.
example example2 and regardless of the size of the browser window was full-screen, while scrolling down the content appeared.
I can't figure out what the problem is. The video is inserted but scaled with the site. That is, in a narrow window, the video is not full-screen and the content is immediately visible.
I just started learning layout, I don't understand everything yet. now the video is like this

Answer 1

Add css property height: 100vh to newHeaderTop class

Answer 2

Maybe a video will help