Complex sentence: After relegation from this level in 2002 it returned in 2005 and, in 2009 experienced its greatest success up to than when it won promotion to the eastern division of the tier five Niedersachsenliga.
Split into simpler sentences: After relegation from this level in 2002, it returned in 2005. In 2009, it experienced its greatest success up to then when it won promotion to the eastern division of the tier five Niedersachsenliga.