Wrong sling and missing sight cover - even the way he is holding the rifle is anachronistic, usually the magazine or hand guard is utilized, gripping the mag-well, thumb wrapped around - while thumb supporting the receiver left-side, while sometimes encountered in period images, is a more modern discipline.
I looked up the Militärarchiv Potsdam, it's a post-war archive, with a lot of post-war information - did they have text with this image? - the jacket-sleeves seem wrong, too -
Also, the finish on the receiver is not consistent with wartime images - where, bluing/phosphate is usually relatively new - you'll see scratched and worn hand guards, but rarely white metal showing through bluing on the receiver itself - of course, i know there were white metal/lacquer receivers, the pictured MP44 is not one.
I would be interested to know, as the photo itself seems genuinely old 1950's or so, a slower lens, as opposed to a modern fast lens that has been graded with a filter.
Regardless thanks for posting.