Well, Sport Warenhaus appears to be some sort of German department store. And Steffl is a Viennese department store. Gerngross group appears to be the Sears of Germany, or they were at one point.
So you've got a vintage German box store folding bike. To figure out who made it, you'll need to do a Google image search for folding bikes. Perhaps vintage folding bikes. The frame design is common, the downtube shape somewhat less common. That should get you pointed in the right direction, unless you find more info on the bike itself.