I would never let me dog off lead unsupervised or where the situation cannot be controlled.
Do you have a fence? I'm guessing no. Your dog should be leashed 100% of the time.
What if it ran into the street and got hit by a car? And don't say that would never happen. Because I'm sure you never thought your GSD would never run after someone.
Fence your yard or leash your dog. Don't be that person.