Are the stairs carpeted?
If so, leave him up there and he'll eventually come down on his own.
Lisl had a 15 step flight of carpeted stairs mastered at 8 weeks.
It could be dangerous for him if they are not carpeted. If you've ever seen a German Shepherd, or practically any dog for that matter on a hardwood floor you'll see them sliding around like they're on ice.
Bear, Anna, Molly, Ossie, and The Countess Lisl von Schlaf
An Unhappy German is a Sour Kraut!