How to change the height of the top bar/header background

This is a very beautiful theme. Thanks to the author.
Now I have a question, how to decrease the height of the black bar on the top? It seems too high to be harmonic with the whole page, especially on my website?
Does anyone know how to change it from the code?
Thank you all.

You need to change the padding for .site-branding and .main-navigation li.

Thanks very much.
It needs to change two parameters to decrease the height. It has taken me hours. Thanks again. I am a freshman on it.