There are also other possibilities why they preferred English (Swiss here, so take it with a grain of salt when I refer to Germans). To show off their English

There are also other possibilities why they preferred English (Swiss here, so take it with a grain of salt when I refer to Germans). To show off their English skills. Although this can even happen when their English is worse than your German. Especially Germans are really proud to be "international" even though it's not always justified. Or they don't want you to stagger about in a language you don't know very well. So some want to be polite and spare you the trouble to speak it. Of course that doesn't help you but you should then insist and say something about "learning this beautiful language" and then usually they can't deny you this. In IT it's quite custom that anybody speaks English when somebody is around that doesn't speak German as you are expected to know the language well enough. After all in IT, you need English every day. For Zurich, which has a great number of foreigners, this applies as well. For Switzerland in general, remember that the Swiss dialect is quite different from Standard German and there are many Swiss who are not that comfortable speaking Standard German so switching to English is an option when they actually don't want you to notice how bad their German is.