East germans have significant slavic ancestry, autosomally anywhere from 25-60% depending the person and region. Slavic tribes were all over east germany historically. Also many east germans and germans are the descendants of germans who lived in central/eastern europe before ww2 and emmagrated to germany as the soviet army came through. Those germans many times were just germanized local slavic people. So yes many germans have slavic ancestry. And as a northern slav you do have genes in common with baltic people, maybe not as much as belarusians but all slavs carry baltic type genes in them to some degree.