I have the same problem on my screen, which is set to 1360 x 768, and I too would welcome being able to hide the top and bottom banners.
Maybe KA staff could add this to the list of user-requested features if/when they redo the interface.  (I doubt this will happen within the next year or two.)

I'd like to be able to hide the parts that are x-ed out in orange (2 banners on top and the "Up next" button on the bottom)

Hi there,

Thank you for sharing your suggestions to hide banners while taking exercises. I will make sure to pass this feedback along to the appropriate team so we can discuss it. 

Warm regards,

Please not just while taking exercises, but also while reading articles and working on programs.  Losing 20-30% of the screen height is a lot.