Complex sentence: The Katowice urban area consists of about 40 adjacent cities and towns, the whole Silesian metropolitan area (mostly within the Upper Silesian Coal Basin) over 50 cities/town.
Split into simpler sentences: The Katowice urban area consists of about 40 adjacent cities and towns. However, the whole Silesian metropolitan area (mostly within the Upper Silesian Coal Basin) consists of over 50 cities/town.