Sounds like you visted a rural area maybe in the former GDR? Definitly not a normal expirence.
Yeah in my experience pretty much everyone under the age of around 40 in any major city speaks English there. Cities like Berlin sometimes it seems like half the people there don’t even speak German haha
When I lived there in the 80s to mid-90s most people I encountered didn’t speak much English. I’ve heard it’s different nowadays.
Zeuthen was technically in the DDR but it’s also a satellite city of Berlin, so I’d expect more English proficiency. Even if you go to the most provincial shit kicker town in Norway, Sweden, Denmark, the Netherlands, Finland every homeless alcoholic or heroin addict is at least bilingual but my experience in Germany was that outside tourist traps you’d be lucky to get a couple of sentences out of anyone.