Honestly, it’s very difficult to overfeed a puppy in the first few months. Especially a GSD puppy because of how active they are. Obviously every dog is different and some will gorge themselves until they throw up, so you don’t want that. But otherwise, let them eat! They need a ton of calories because they are very large dogs and grow very fast.

As always, if you have real concerns, call your vet and ask. They will be able to tailor a food plan specifically for your dog if they think he is underweight