That would mean taking the header out of the site container, which would require advanced editing of the php files. You will need to get a developer to help you with that as it is not a basic customisation
laranz: It was an example of how I want it to be, anyway I managed to do this.
header is not in <div id=”container”></div> + custom css: .header-wrap{margin-bottom:30px !important; z-index: 1000}
moreover, I had to disable search in the header