If you're ever curious and want to do a deep dive into the OSS most of their training videos have been uploaded to youtube. It's pretty fascinating stuff and "Keeping it simple" was a big part of developing a false personality!

Also German? Polish?

Dick's Mother (Rose Kowalski) is from the Silesia region, which has a complicated history. https://en.wikipedia.org/wiki/Silesia. So she is Polish or German depending on who is talking about her. German is her predominant language, but she also speaks Polish, and passable English. It doesn't come off in dialog as much as I'd like, but it's resulted in Dick having a mix of Minnesota (From his father Rhett Kowalski ) and German accents and it's only going to get more pronounced.