Good afternoon Jim,
Three months. A baby. A human child would be less than 2 years old. A bit early to be expecting training compliance. Realistically think two steps forward and one or two steps back for awhile.
My daughter has a high drive female GSD puppy, a month or two older than yours. I get to puppy sit Xuzu several days a week. She wants to play with, mouth and bite tug the leash. We are working on NO. Sometimes successfully, sometimes not so much. But NO is consistently used to dissuade unwanted behavior.
A log learns a lot with its nose. A baby is learning everything. The dog learns of visits by other dogs by smelling where they marked. It is a good idea to let the young dog smell on a walk. The wee dog is exploring its world, and that is perfectly normal.
Human babies struggle to explore and often don't want to be restrained.
You deal with the behavior with patience and purpose and lots of rewarding talk to the wee dog, and no frustrated corrections or loud voice commands. In my opinion.
One excellent side benefit of having a puppy or an adult dog is that you have to learn and practice patience even when frustration wants to burst forth. Stay positive. You took on a huge responsibility and now you got to stand to.
I usually try to laugh off frustration, and loosen the leash. A puppy wants to bond with you but it wants to explore. Patience and consistency, and lots of verbal rewards. Don't over use treats or the dog trains you to feed it. Tactile rewards are probably the most valuable tools I use.
I've had a bunch of GSDs over the years. I have a few now. They have all got different personalities. The more you interact with the dog, the more you figure out what motivates the dog to comply with your expectations.
Each dog person has their own view of how to work with their dog. For example, I feed kibble, so I use it as my training treat. Occasionally, infrequently, I offer a more treat treat but not enough so that the dog or dogs will expect it and only work for it.
If you are walking and the puppy wants to go left and you want to right, stop, kneel down and pet the dog and talk blather to the dog, It gives you time to refocus frustration and have a tactile interaction.
If you practice marker training, you will enhance your bonding with the dog and be amazed by the progress you can make with the dog, as long as you keep your expectations reasonable. Marker Training. Gleeful verbal rewarding for the smallest of successes. Forgiveness for relapses.
I'm curious, is this your first dog? In any event, keep the dog around you as much as possible. Crate training not withstanding, the more the dog is around you casually, the more the bond becomes strong.
The old adage, you train the dog today for the dog you want tomorrow. The more you work on bonding, the more you will have the dog you want tomorrow.
Create a diary, with training activities and repetitions and successes and unwanted outcomes, and set reasonable training times. A young dog has the attention span of a gnat, so just enough training time to keep its attention, and enough to mitigate your frustration.
Dogs on my mind. I would encourage you to lighten up. Before your dog can be trained, you first have to be. Frustration can lead to revenge corrections in a worse case.
Sorry for the long two cent response to your post.
Mike A.
"I wouldn't touch that dog, son. He don't take to pettin." Hondo, played by John Wayne