@oristarA,
He almost certainly came to the US in his late teens, early 20s, so the window of language opportunity had pretty much closed and there almost certainly will be aspects of his language, especially spoken language, that will mark him as a foreign speaker for the rest of his life.
I say this not to denigrate, that's just the way it is. Henry Kissinger arrived at about age 16 and he has never been able to lose his accent. His younger brother was 13 years old and he has no accent, he sounds just like any other native speaker.
He will turn around/confuse the odd phrase or two because of the influence of his mother tongue. You might be able to see instances of that better than I, Ori.
I wasn't able to discern what "the beings" means but that may well be a known to those that surround him, those that share his field.