The main language in the Bundesliga is still German, but since there are more and more intentional players English is also a very often used language. Communication is very essential in soccer and English just helped to overcome misunderstanding as long as players are not confident enough to speak German.
Der Klassiker in German (The Classic), also known as the "German Clsico", is the name given in football to any match between Borussia Dortmund and Bayern Munich.