That little piss-ant stuck his nose into someone elses business. Simple as that. And I bet in that situation being half the size of the German business man, he realised that taking it any further would have been a serious mistake.
My German isn't the best, but it seems like he was talking about how much money was spent on revamping the building in that business district and the scrawny little fugger was like "What's going on here"
The Kraut businesssman simply asked if there was a problem with what he was doing and the runt must have ojected. So "wham" he clapped him and told him to scram.
IMHO an awesome move!
