The GSD, unfortunately, has a reputation for being aggressive. This is true in all dogs who have not been trained or properly socialised. A Jack Russell is more likely to bite you (they are aggressive, ankle biting dogs in general) than a GSD.

A GSD is not for first time owners. They are a highly demanding breed, need lots of exercise and lots of mind stimulation to keep them from becoming bored and thus, destructive. A game of fetch is simply not enough for this dog; why not try scenting with them?