2. what was the nazi-soviet pact? why did hitler make a deal with the soviet union?

This pact is called the Ribbentrop-Molotov Pact, after the Ministers who signed it, and it was officially a pact of non-aggression between the two states, but additionally it shared the lands between them among the two powers, the Soviet Union and Nazi Germany. This included splitting Poland in two.  Hitler made a deal to know that Russia won't stop him and that he can focus on invading Europe without fearing an attack from Russia, for the time being ( Germany broke the Pact later, when the time was good for them to fight Russia... but they lost anyway).