Hi,
with this Layout "Stripe Responsive", the header image will always be scaled, so it fills (and is centered) the entire header-area. Playing with the "Breite" and "Höhe" Values in the "Kopfgrafik"-Section of the Layout-Settings might achieve what you need. Otherwise, you must probably pick one of the other Responsive Layouts like e.g. "Producer Responsive" which has a Kopfgrafik-Setting to either scale or center the header.