2019 – White space between header and body

Hello

I am trying to tweak a site using the twenty nineteen theme.

There’s a lot of space between header and body. See the image:

WordPress twentynineteen default space

I’d like to decrease it to about 1/3rd.

I cannot find where to do it. I am guessing style.css. That did the trick for my headings h1-h6.

Thanks