I just want to add that yes, this breed is very easily trainable, they seem to get things right away. But they do need a good amount of exercise and discipline. They will test you as they grow older. It will be a while before the puppy matures to a stable and calmer temperament. A trainer said to me that a GSD is a very hard dog to have even when you are exerienced with dogs, because they can have issues without a thorough and appropriate socialisation process, and it is time consuming.
All that said, they are very loyal and loving and love to please.