No.

Many are, especially higher level courses (ie, above the Bachelor level), but not nearly all of them. Some lecturers try to hold their lectures in English even though they speak it very poorly.

Pretty much all lecturers will happily take English questions and answer them in English. And all German comp sci students speak English.

For many courses which are held in German the materials are still in (some kind of) English. You can usually get by very, very well by skipping the classes entirely and learning from the provided materials only. In fact, that's what a large number of German students are doing too.

No, it depends on the university. The predominant language of teaching in undergraduate courses in Germany is still German. However, the amount of course offerings in English language is increasing. The most common model now should be that a few classes each semester are being offered in English, which are often being taught by visiting professors or guest lecturers.

There is an increasing number of German universities which offer Master programs taught in English.

Here is a list of the Deutscher Akademischer Austausch Dienst (German Academic Exchange Service):

> https://www.daad.de/deutschland/studienangebote/internationa...

As the other repliers already said, the amount of English classes is limited, though you should be able to get your Bachelor without having to take German courses. That, of course, will be a bit harder to find the right lectures etc