header image sizing in twenty seventeen theme

I've seen some posts about resizing the header image but haven't managed to get anything to work.

I want to reduce the height of the header image on the homepage as it takes up about 50% of the window height (please see homepage.jpg)

My other issue is with the header on the main pages, while it is a much better height, when the widow is resized the background image is cropped.

I'd ideally like to have the logo separate to the background image on the main pages as it is on the homepage, but can't work out how to do it without having the massive header.

is this possible to do/ (I don't have any real knowledge of CSS.

Thanks