A question about being bi lingual

In the USA most of us have never mastered anything but English. You may be taught other languages in school but if you are never immersed in them for any period of time you never feel comfortable reading, writing, or speaking a foreign language. My unscientific observation is that most Germans are fluent in both German and English. In Germany is English taught in all schools? How do people become fluent in both German and English? If you are truly bi lingual, what language do you "think" in?