Custom header size

Using the hueman child theme I’ve added a custom header background image but it doesn’t show the full image: its zoomed in. Can anyone help? I also would like it so the image doesn’t go onto the top menu either.

Currently using this on the CSS Stylesheet:

#header {
background: url(https://chriswhitley.co.uk/wp-content/uploads/2014/07/film-2-e1433258971334.jpg);
background-size: 100% 100%;
}
}

Site here:
https://www.chriswhitley.co.uk