I've heard that Poland had decent relations with Germany until the latter 1930s. Britain and France encouraged Poland to take a hard line with Germany, promising to back Poland in case of war. (Much like the U.S. encouraged Ukraine to stand firm against Russia.)
After the war, Britain and France abandoned Poland to Soviet occupation, reneging on their promise to preserve Polish independence.
It’s true that originally Hitler saw Poland as an ally because of their hatred of the Russians. But most likely once he used the Poles to help defeat the Soviet Union, he would have turned on them.
Poland and Germany did not have “decent relations” during the inter-bellum years.
There was a customs war from 1925-1934 and the Chief of the German Army Hans von Seeckt stated: “Poland’s existence is intolerable and incompatible with the essential conditions of Germany’s life. Poland must go and will go - as a result of her internal weakness and of action by Russia - with our aid.” (Sword and Swastika by Telford Taylor, London 1953).
The Germans never accepted that the chunks of Poland they took in 1776-1791 could become independent
you say “Poland took a hard line” - that’s the same BS argument that is being made against Ukraine today.
The Germans did not see Poland’s existence as legitimate and wanted to absorb her.
As to “After the war, Britain and France abandoned Poland to Soviet occupations”
Quite frankly - what could the Brits and French have done even IF they had the political AND social will to do so?
The Soviets were already in most of what became East Germany, so the UK+French would need to battle a massive Soviet army back to even read the Polish borders. That was flatly impossible without American support and even WITH American support it would be nearly impossible