The German borders changed a lot after '45, so what happened to the ethnic Germans who were living in modern-day Poland, Volga regions, or the Baltic states?

I'm looking at this infographic of German populations in the early '40s. As you can see, there was the NE part of Germany, which is modern-day Poland and Baltic states. In '45, the borders were redrawn, so what happened to these ethnic Germans? Did they migrate back to Germany, and if so, did they just settle in the Eastern parts of Germany, or were they dispersed all throughout modern-day Germany?

Also, were these ethnic Germans in these lands outside of modern-day Germany assimilated to Russia, Poland, Baltic States, and Romania, or did they assimilate with the NSDP in '41?