Complex sentence: Before it meets Danube, Velika Morava splits, creating 47 km long arm called Jezava, which flows into the Danube separately, in the town of Smederevo, and it's joined by longer (51 km) river Ralja, from the left.
Split into simpler sentences: Before it meets the Danube, the Velika Morava splits, creating a 47 km long arm called the Jezava, which flows into the Danube separately, in the town of Smederevo. It's joined by a longer (51 km) river, the Ralja, from the left.