welcome to Cruise-Chat.com.
As for Warnemünde: The port is more than 150 miles away from Berlin. The railway station is right next to the pier, however, so it's an easy ride into the City of Rostock, to which Warnemünde belongs. That is if you actually dock in Warnemünde. If it's a busy day with several cruise ships in port, the ship might dock in Rostock's "Seehafen", instead.