Complex sentence: The stadium is the second largest in the city after Berlin's Olympiastadion with 20,000 seats (15,000 covered) and is used by football sides Hertha BSC II and BFC Dynamo.
Split into simpler sentences: The stadium is the second largest in the city after Berlin's Olympiastadion with 20,000 seats (15,000 covered). It is the current stadium in use by Hertha BSC II and BFC Dynamo.