Kalkhoff Vintage Bike

Hi All

I've found a very interesting bike in the trash bin during my summer vacations, which seems to be a vintage Kalkhoff.

The bike is equipped with a Sachs Torpedo Duomatic rear hub, and from what I've found so far, it must be from late 70s to early 80s.

Another interesting aspect is that the frame isn't foldable, but instead it splits in two halves.

I would appreciate any help from someone more knowledgeable than me to identify the manufacturer, model and other stuff