More edits and suggestions -- with some of my long-winded (and less important) comments in small text, to save space!

‘Don’t touch the curtains,’ Peter said, ‘you can might give us away with the heaving movement.’
As Ramil said, "movement" (or "motion") sounds best here. "Heaving" suggests the movement of something heavier than curtains -- like a woman's breasts when she's crying. Seriously -- Google for "heaving" and "bosom"!

She nodded and peered into through (or: "out") the window, trying to comment on what was going on outside.
You can only peer "into" a window if you're standing OUTSIDE the house!

‘He says the invincible German army is now approaching -- well, his Russian isn't very good, but he talks about brutally crushing weak...
I suggest this small addition just to make absolutely clear for the reader that the speaker is a German invader, not a Soviet traitor! It also helps to emphasize that the speaker switched languages when he got to "half an hour for amusement".

'...we are now slaves of the Umm... "People of the highest level", maybe...'

'Overhuman, above-human Übermenschen, super-humans, I got it, go on.'
Even if he doesn't speak German at all, Peter is definitely educated enough to be familiar with the Nazi expression Übermenschen and the antonym Untermenschen, and to know that they respectively translate as "super-humans" and "sub-humans."

Also needing no explanation for Peter or English-speaking readers (because they're heard so often in Hollywood movies about WW2!) are German expressions like Achtung!, Schweinhund, kaput, ein, zwei, drei, ein Führher, ein Volk, ein Reich, Scheiße -- and of course "Gesundheit!" when somebody sneezes. (Although Gesundheit! may have been popularized in English by way of Yiddish, and not directly from German.) All of these would normally be italicized in English text, by the way.

'...slaves of the Germans who are the only God-chosen people on the planet...'
Peter, as an English speaker, would tend to "hear" the word "God" as capitalized when the monotheistic deity of Abraham is referred to, whether or not he's a religious believer. The phrase "Red Army" should also be capitalized in English, by the way.

'Nazis,' Peter shuddered, 'I've heard Jews were claiming the same’'doing a really sick parody of Jewish Scripture.'
Caution: Any type of comparison between Jews and Nazis must be phrased with extreme tact to avoid accidentally offending your readers! Here are my thoughts on this delicate subject:

Both the Jews and the Nazis may have seen themselves as "God's Chosen People" (and quite possibly the Flying Spaghetti Monster, may His most holy noodles be blessed, doesn't agree in either case!) but there's one VITALLY important difference: even in backwards Old Testament times when the Jews were stoning blasphemers and homosexuals to death and slaughtering "Amalekites" left and right, Judaism recognized that a foreigner/pagan could freely choose to make a religious conversion, accept YHWH as the One True God, and become a "full Jew."

No such conversion was possible under the Nazi regime, however -- large numbers of baptized German Christians who were only 1/4 Jewish by blood, and who knew absolutely nothing about Jewish religion and customs, were taken to the Nazi death camps -- that's why Israel's "right of return" law is written the way it is.

With the result that Israel has sometimes had a bit of a problem with anti-Semitic Soviet "refugees" who were allowed to immigrate because they happened to have ONE Jewish grandparent! And, incidentally, Jews have always believed that non-Jews of good moral character will be welcomed by the Jewish God (i.e., the ONLY God) into Jewish Heaven (i.e., the ONLY Heaven). Admittedly, there are some Jews who use the word goyim as though it were a slur, thinking that non-Jews are inferior in God's eyes -- but Jews who look down upon Gentiles in this way are BAD JEWS, ignorant of how their own religion actually defines the concept of "Chosen People."

And although Peter's own upbringing was Christian, and perhaps he doesn't know Jewish theology very well, he's certainly aware that Nazis, in the end, will get melted into bloody puddles of goo by a very pissed-off YHWH, as was realistically shown in the 1980 documentary Raiders of the Lost Ark.))))))

In short, Jewish religious law has allowed since ancient days that a non-Jew can "choose to become Chosen" by a personal act of free will. But the Nazis -- obsessed with race-purity and their own comical misunderstanding of Darwinian evolution -- didn't see things this way.

So, in summary, I think that calling the German guy's speech "a sick parody" of Jewish thinking will work very well here, and won't offend anyone (except for neo-Nazis, of course -- but they're a bunch of pencil-dick no-balls losers, so one should strive to offend them whenever possible!)