and how is Poland only 0.07% ethnically German?
The evacuation of East Prussia was planned in late 1944 and executed in 1945. Prior to the official evacuation civilians were ordered shot dead for fleeing as it "undermined military morale". The evacuation of Ostpreußen begins in late January 1945 and is considered one of the larger exoduses of people in human history with the population in Prussia dropping from 2.2 million to just under 200,000.
During "Fall Hannibal", led by Karl Dönitz, any and all naval resources, military and civilian were used to evacuate refugees across the Baltic Sea to Western Germany and German-occupied Denmark.
If you'd like to read more on the subject a good place to start are the memoirs of Dönitz himself, or a book called: Steel Ships, Iron Crosses and Refugees by Charles Koburger
There was a massive post-war resettlement plan - in effect, ethnic cleansing - in which ethnic Germans were forcibly expelled from Poland, Czechoslovakia and other countries and resettled in Germany. These people were not necessarily Nazis, but long-standing German populations who had been there for centuries. This chapter of history is quite obscure today since it somewhat complicates the narrative. For more:
My grandfather (who was German) as a young boy was evacuated from Silesia to Berlin, and then in 1960 he fled from East to West Berlin, because he didn't like the GDR, and was then resettled to the black forest. That's where I was born in 86, but all my direct family on my fathers side were either born in Berlin or further east.