Hi Hedi
This is a bit of a tricky one as you are using the header slideshow area to contain your logo rather than the logo image/text. The header slideshow displays the image in a cover format so the area is always filled by the image regardless of the image size/ratio. This does cause to often cropped.
To amend try adding the following to the
Responsive Custom CSS fields within the
General -> Responsive Options tab of your template settings. For more details on using these fields may I suggest the following article...
https://joomla51.com/tutorials/template-parameters/applying-custom-css-to-a-screensize-device
(you may need to experiment with the sizes)
#container_header {
height: 100px !important;
min-height: 200px;
}
Ciaran