Der Film Nr. 1, den man sich als Pole ansehen kann

Boring as shit

Every Polish person (and any person who cares about Europen history) should know the history of Katyń, but not necessarily from this movie.

#1 in my opinion should be about out identity, and satyrical movies are great at depicting that.
Dzień świra is a strong pick, I’d say Jak rozpętałem II wojnę światową is also a good one, maybe Rejs or Miś but you need some context for them

This and Wolyn

And when it comes to the best Polish historical series: „Pogranicze w ogniu“

Kanal was better.