Slavs in East Germany

What information do you haveon what Slavic peoples were where in what
until 1990 was East Germany? I heve heard of: Obotrites or Obodric^i
in Mecklenburg; Havolane and Sprevjane in Brandenburg (named after
the rivers Havol and Sprevja, now Havel and Spree); other peoples in
the south. Another source mentions a people called the Wiltzes.