In Russia, I never saw anybody playing the board game "Big Brother Pilsudski"

If we compare Stalin and Pilsudski, what they most have in common is a mustache. I am not saying that Pilsudski was a saint (he pursued a rather controversial policy towards the opposition), but he is in a completely different league.

we remember how Poland was eager to become an ally of Nazi Germany and take a part in forthcoming war against Russia;

When exactly? The facts are that Poland refused in 1939 to join Germany and participate in any aggression against the USSR. Do you mean to say that on September 1, 1939 we were attacked by an ally?

It was different with the USSR. The Germans and Soviets first agreed to divide Poland and then worked closely together until 1941.

Below are some photos from 1939. The Germans and Soviets do not look like enemies.

how it stole the Teschen region from Czechoslovakia during the Munich Agreement;

Poland was not in Munich. Poland took only those territories where Poles were in the majority. But I agree, it was controversial. Especially the policy of retaliation (we did not have good relations with the Czech people).

how it staged a coup d'etat to annex Lithuania (unsuccessfull);

It is more complicated because Lithuania did not want normalization of diplomatic relations. The effect of this long conflict was that a year later "evil Poland" disappeared from Vilnius, but Soviet Union deprived the Baltic countries of their independence and later sent hundreds of thousands of people to Siberia.

The concentration camp in Bereza Kartuska, of course, served far fewer people than the Gulag archipelago in Russia, or the German WW2 camps, but this is simply due to a smaller country size.

C'mon. We can't compare it. In Bereza, about a dozen people died. Less than 0,5%. In the gulags, millions.

One may find many interesting facts in the history of any country, the main thing is not to turn away and not to close your eyes (look here, but don't look there), and correctly evaluate what you see.

I agree. Nothing is black and white. That's why, for example, I don't blame the Latvians for joining the SS after the horrors the Soviets did to them. It's just important what sources we use.