The background image is already set to cover?
The problem is that your image is not wide enough at 1280px - it needs to be 1950px so the "cover" is upscaling your image to fit the width which obviously means that the image gets taller too (to avoid distortion).
So, I've suggest that you just alter your image size to 1950px x 1024px.
Well, the image does not get displayed completely. The cover does not work right, because the cover does not show the lower part of the image, which works in a another template correct. The hole images gets displayed and scrolled correctly with strechting or shrinking it to the needed size.
not in your template.
Same for the news silder.. Here the upper part of the images is cut off.
Get the images in Full size and you can see what i mean