Hi Matt, quote from Wikipedia:
Karlsruhe was decommissioned on 16 June 2017 and handed over to Wehrtechnische Dienststelle 71, the navy's technical weapons research division, for use as a trial and target ship. After being fitted with sensors, she is slated for disposal in 2018 in a series of tests to determine the effects of various munitions and weapons, particularly those used in asymmetric warfare, such as smaller weapons and rockets currently used by terrorist and pirate groups in attacks. As of April 2018 Karlsruhe is moored at the naval arsenal in Kiel.

What would they like to do with these decommissioned Navy ships? Why take so long to remove?