Header background height change and add header image

[worldwideunlock]

Hello,

How to change header backgroung height and how to insert a header image?

I was able to edit global and header background added but can't find the solution how to make it higher, it's to small and I want it bigger.

I also want to add an image into the header that would go over the background. I can't find any height definition in global responding for the header. Using presta 1.6.1.24. Please help me with that.

My website is here: https://bestphones4u.co.uk/

Global.css that I edited :

header {
  z-index: 1;
  position: relative;
  background-image: url("/img/header_bg.jpg")!important; }

[worldwideunlock]

I made some changes to global css.

Added definition

#header {
  height: 500px;
}

so now header is bigger