What exactly were the relations beetwen two countries in the interwar period? From my understanding they improved significantly after NSDAP came to power, they even signed a non-agression pact and Poland participated in partitioning of Czechoslovakia. Did Hitler really want Poland as an ally or was this some sort of deception?
No way in hell.
In my opinion, as how I perceive it
Poland was Hitler's start of expanding. He needed a corridor to invade the USSR, as he had made it no secret of his hatred towards communism. There was quite the row between PL and D about gaining access to Prussia (modern day Kalliningrad Oblast and Mazury and Klaipedia areas (Memel)) as it was not linked to Germany by road, and they needed to pass through Poland. The Free City of Danzig (Gdansk) was also a friction point between the two.
This is logical as well. For example, Pakistan needs Northern Kashmir to maintain its connection to China, the Trans-Karakoram Highway, India needs it for Afghanistan, needs Sikkim to maintain connection with NorthEast. There are many live examples of this today.