From: Sydney, Australia
It depends on whether you mean "Germany" or "Hitler".
Joe Average German (or Karl Mittelwert Deutsche) couldn't give a toss about Poland. Most of the population of West Prussia, that part of Prussia ceded to Poland after WWI was not ethnically German, whereas the population of East Prussia had an ethnic German majority (as did the Sudetenland). Most Germans wanted land access to East Prussia -- these days it would have been solved by building some kind of 8 lane superhighway with truck stops et al, but it wasn't a high priority issue.
German nationalists, stirred up by Hitler, definitely wanted all of Prussia back. Along with the Sudetenland, chunks of Alsace/Lorraine and parts of southern Denmark. Sure, Hitler and the German nationalists regarded the slavs as untermenschen and the historical relationship between the teutonic tribes and the slavic tribes going back over a thousand years was one of master/slave race, but most Germans had gotten past that.
At a diplomatic level, tension existed between Poland and Germany over a number of issues wider than the Prussia/corridor issue, however there was German support for Poland in the resolution of the Poland/Lithuania dispute of 1938, and the Polish annexation of Bohumin in Czechoslovakia. So it's difficult to say whether Poland was or was not an enemy of Germany in 1939.
As a hypothetical answer to the second question, a Soviet/Lithuanian alliance existed since 1920, there was enmity between Poland and Lithuania and also between the USSR and Germany, and so if the Soviets invaded Poland on the pretence of assisting Lithuania, it may have been the case that Germany would have assisted Poland. However as others have pointed out, the USSR was in no state to do that.