serious problem with header

Hello Skandha, I have a serious problem with the header image. Most images have the prescribed measures 640 x 480. If I use such an image as a featured image in combination with the css you gave me, the result is a very high image. You can see it here. (staging.toerfietsleusden.nl/service). If I make with the css for a less width image the image less high, then the proportions aren’t right anymore. It looks like a distorting mirror. Images with 1900 x 800 px are not very much on stock, because most images are made with smartphones. I tried to use the header image only on frontpage and use the cover image. The result is almost the same. You can see this on the same page. Can you please give me a clue to come to a solution? Kind regards Hans Hagmeijer