Thanks for your quick answer, but that’s not what I am really looking for.
The Revolution Slider has the possibility to keep the aspect ratio of the slider images.
Because of the fixed height in the woodmart slider, the height is on every screen size the same, only the width is changing and adaptive. Is there a way to keep the aspect ratio of the images of the woodmart slider (owlCarousel) when I use the featured image (=background image in css-code) for the slider images?