Germany

English is a mandatory second language in virtually all levels of education in germany. This hasn't always been the case, so the ability is more widespread amongst younger generations.

It is also worth noting that due to the way we learn english (primarily by reading/writing and possibly listening) those disciplines tend to be much better developed than actually speaking the language, simply because we rarely get to in everyday situations (and if we do it is almost always with another European national who has learned the language the same way we did, and struggles the same way).

On the other hand, this often leads to Europeans correcting english speakers on their grammar, because native english speakers learn the language primarily by hearing and speaking it, and there/their/they're and such sound way too similar.

My German teacher in high school (80’s) told me he knew he was fluent, or something, when he started dreaming in German. Also taught Russian. In the 80’s. Stories were very interesting.

First of all, not everyone thinks in language. A lot of people think in abstract concepts they only materialize into language when they need to output them. For them, the question is moot.

Second, it’s highly context dependent. In situations where you speak language A, you’ll tend toward language A, and vice versa for language B.

That said, I can assure you that 99% of Germans are NOT bilingual with English, despite being fluent. Think of it as C1 in the Oxford scale, with very few on C2.

Most (educated, young) Germans speak some English, relatively fluent if they use English frequently at the workplace or in their free time (e.g. movies). We are not bilingual. English is a language taught in school (for most) and learned after childhood.

Actual bilingual people, such as a person from the UK growing up in Germany, can have two mother tongues. Someone who actually lived in an English speaking country for more than 1 year may be bilingual, but the average German is not.

To answer your questions: Most schools teach English as the first foreign language and any school teaches at least one foreign language. So, yes, every German should at least speak one other language and very often it's English. None of our neighbouring countries speak English, so French is also popular, but declining. Spanish is popular, but nowhere near as widespread as English or French.

And on your second question: I think in language and most of the time I think in German, but when I'm in an English-speaking country or working with English texts I tend to think in English.