Language
They must have smuggled in a universal translator from Star Trek. How else did people of various nationalities easily and quickly communicate with each other?
shareA good question. In historical fact Alan Arkin's character could speak Russian. So he could communicate with Sasha, a Russian Jew, who did not speak Polish or Yiddish. Many Jews, even from Holland, had some grasp of Yiddish which could serve as a common language uniting Jews from different parts of Europe, though not all Jews knew it. Yiddish is also somewhat like German, so German-speaking oppressor and Yiddish-speaking oppressed could communicate to an extent.
Some inmates who knew languages acted as interpreters, and sometimes this usefulness contributed to their survival.
The film doesn't make it clear but in the original book on which Schindler's List is based, the Russian officer who rides up to the prisoners at the end at first speaks in Russian, which is only semi-comprehensible to them. Then he turns out to be a Jew and starts speaking to them in half-forgotten Belarusian Yiddish, which they understand much better.
"Chicken soup - with a *beep* straw."