Complex sentence: It is arguably the tallest office building in Brandenburg, with a mobile telephony mast reaching 95 m; however, its roof height of 89 m is 1 m less than that of the Stern-Plaza in Potsdam, built in 1998.
Split into simpler sentences: It is arguably the tallest office building in Brandenburg, with a mobile telephony mast. Its roof is less than that of the Stern-Plaza in Potsdam, built in 1998.