including a lot of arts and treasure like the Berlinka treasure it has legally speaking no right
Well, law is either ambiguous as to it or not very clear on the issue. Depend who is a paymasters of a lawyer. In other words the law is not clear black and white on it!
On other hand if we talk morals, fairness and all that - Germany has not ground to ask for it. Amount of art destroyed and stolen by the German side is such that Berlinka doesn't even came close to amend for that. There is still plenty of loot from Poland in private German hands including my great grandma gold watch. Somehow the 'German side' cannot deal with it at all and let it go in regard to Berlinka.
but Poland received more than other countries
That is blandly untruth. Didn't you say yourself how much the Soviet union extracted from Germany on the top of acquiring some German territories?
you can't reasonably expect the great-grandchildren to pay additional money for the crimes of their great-grandfathers
I can reasonably expect a reasonable and fair compensation to be paid. Not some excuses and taken money.
As great-grandchildren paying for the crimes of their ancestors - pry tell when Germany has paid to France the last rate of the compensation for the war? (even IWW if I'm not mistaken) was it last year or was it 'only' a couple of years ago? Is that reasonable and if it is reasonable in case of France why it isn't reasonable in the case of Poland.?
I think that general awareness in Germany as to the severity of the German occupation of Poland and amount of ruins, dead and misery it had left behind is grossly underestimated. I find it mildly repulsive. It seems to me there is a purposeful policy in Germany aimed at playing it down or/and whitewash it when it comes to Poland.