German is regional
Hochdeutsch (Standard German) is what schools teach; Austrian German and Swiss German vary substantially. Standard German understood everywhere; specific city dialects (Bavarian, Schwäbisch, Plattdeutsch) emerge in informal speech.
Berlin
Berlin Goethe-Institut Berlin, Sprachschule did, Berlin Sprachschule. Berlin German — direct, sometimes blunt, occasional Berlinerisch slang. Strong international student community. Mitte or Kreuzberg base.
Munich
Munich Goethe-Institut Munich, ASKI, Sprachenatelier. Bavarian accent intrusive informally — Standard German taught in school but locals speak Bayerisch socially. Higher cost of living than Berlin.
Vienna
Vienna ActiLingua, Hardly know German. Austrian German has distinct vocabulary (Erdäpfel for potato, Jause for snack), softer pronunciation. Useful if you'll be working in Austrian/German-speaking Switzerland later. Innere Stadt classical setting.
Hamburg
Hamburg Goethe-Institut Hamburg, Berlitz. North-German Hochdeutsch is closest to dictionary-standard. Local Plattdeutsch dialect rare but distinctive. Less language-school choice than Berlin.
Zurich
Zurich Goethe-Institut Zurich, Inlingua Zurich. Swiss German is essentially a separate spoken language; Zurich uses Standard German formally. Expensive (€600+/week courses). Useful only if planning Swiss living.
Strategy
Berlin for affordability + variety; Vienna for Austrian work; Hamburg for cleanest Hochdeutsch. Goethe-Institut certificates standardized across cities. CEFR levels matter more than school for institutional purposes.