The company I work for is quite international. No one on the team is actually German, so I can't say that I know much about the German working culture. However, what I heard from my friend is that German are more conservative, that's why most startup companies are none-German. A lot of startup companies are owned by none-German and usually the employees are from all over the world.
For my company, we have 4 British, 1 French, 2 Bulgarian, 1 Indian, 1 American, and me. (There are few other people but they left) Beforing coming to Berlin, I was kinda stressed because I was afraid of the language barrier. Even though I knew the working language is English, I was worried about being not able to fit in well. It was really lucky for me to work in such diverse company with really relaxing company culture. My friend who works for a company where her colleagues are mainly German is struggling with language barrier.
Based on what I heard from local, it's quite common to work over-time in Germany. People usually don't get paid for the over-time, instead, they would use the overtime they put in for extra vacations.