I had the impression that the assistant's proposed task was to translate von Neumann's older papers, the ones he wrote in German before moving to the US. In ei

I had the impression that the assistant's proposed task was to translate von Neumann's older papers, the ones he wrote in German before moving to the US. In either case, he was fluent in German from childhood, but his English was not all that great at the time he moved (it got better with time). His native language was of course Hungarian.