Spreewald is the best option for hiking in Germany. You can have a countless number of natural hiking trails in Spreewald. It is a hiking and trekking trail which suits for everyone.
From Lubben you can follow the Spree south to Lubbenau and North to Schlepzig. You can follow the trail to the natural trail in west to Lehde, the 'Venice of the Spreewald' with its great Freilandmuseum, which has traditional Sorbian thatched houses and farm buildings.