For the last three trips to Germany, I've bought a SIM from one of the discount grocery store chains (PennyMarkt, REWE, etc) in Germany. With PennyMarkt it's a T-Mobile SIM, resold by the store at about half the price that T-Mobile charges. At the time, because I was using it with an "aircard" or "webstick" with my netbook, I had to make a phone call to switch it over from phone to data. I'm not a German citizen, and I've never had to show a passport.
PennyMarkt's website (www.penny.de) is in Germany only This is their rate webpage. It looks like you can get various plans. One is 100 minutes, 100 texts, and 100 MB of data for 1,99€/day. The SIM is good for a month. Or you can get 500 MB of data, only, for 7,99€ in a month. I don't know about international calling.
I imagine if you find one of these stores in a big city, like Berlin, someone will speak English. After the initial purchase, you can load extra time on the card at any of that chain's stores, but a lot of stores in small towns do not have anyone who speaks English.
You might also find a T-Mobil store, maybe at the airport. It would be more expensive for the SIM, but they might be better at English fluency.