The street sign clearly says "Osterstraße," and the language is German. The "Flohmarkt" poster indicates a flea market in Germany. The architecture and the general urban layout are very characteristic of a German city. I see a "D" sign, which is common for Deutsche Post or similar services in Germany. I am quite confident this is in a German city, likely Hamburg given the street name and general vibe.

I suspect this is in Hamburg, Germany. I am 85% sure.

then: guess