Firstly, it’s the school system. From a young age they are exposed to English literature and media, not only in English classes, but in other subjects such as history too. Secondly, the younger generation seem very motivated to speak several languages, not just English. I spoke with several people in their 20’s and 30’s who could also speak a third language. Thirdly, it's a Berlin thing. As an international city of the world, virtually everyone you meet can speak English. Many people can visit Berlin and speak German Click on the following link to see other reasons people don't practice German in Berlin.
As Berlin attracts more business startups from all over the world, particuarly tech, the importance of speaking English becomes more important.
But what about the loss of the German language? The young Germans have shown that is still possible to retain your mother tongue while using English as the international language of exchange. By being open to speaking English to outsiders Germany welcomes other nationalities to join in with conversations. With this lack of fear, the Germans enrich their language and encourage non-German speakers to learn basic German. Without the fear of losing their language, German culture has embraced English and English speakers who they encounter. It is enriching rather than thining their culture.