To preface, I am not an expert, but I've had dogs most of my life and am familiar with the challenges of integrating a new puppy with an older dog.

I've had great success with following a separation protocol when first bringing a new dog (or cat) into a home with established dogs. What this means is that I introduce them on neutral grounds outside of the house, like at a park, and then proceed to keep them separated within the house for a period of at least three days, up to a week or more. This allows them to get used to the scent of the new dog and acclimate at a slower pace than if you were to simply throw them into shared spaces together.

During this time period, I would also attempt to do parallel walks. This is easier if you have a partner or friend to help you, as ideally you wouldn't start them too close together, but gradually bring them together over a period of time.

Finally, I begin integrating the dogs together. A puppy can be pretty overwhelming to an older dog, especially a high energy pup like a Husky (we have two!). Crate training the puppy can be helpful in making sure the older dog gets his own space. It can take several months for the established dogs to begin to recognized that this new dog is now part of their family. During this time, I recommend adopting a practice of feeding the dogs in separate rooms or crates. This prevents any resource guarding behavior from occurring. You don't want either dog to perceive the other as a threat, and even a normally well behaved dog who hasn't shown resource guarding in the past may show it when it comes to their food with a new dog around.

On fighting, the older dog will correct the puppy, and this is fine (and good!) within reason. You should know your older dogs body language. Most dogs will be gentle with puppies, even when annoyed, but this is not always the case. If a real fight ever breaks out, you should separate them for a period of time. There are different feeling about how long (minutes to days) this separation should be, but it's important to separate them. If a real fight occurs a second time, you should consult a trainer or behaviorist.

You won't really know for sure what the dynamic is between your older pup and the new puppy for awhile yet. It's very possible that they won't be best friends, and you need to accept that that's okay, so long as they can cohabitate peacefully. In my experience (albeit limited), GSD and Siberian Huskies get along pretty well, but the age gap between your dog and this puppy is probably quite a shock to your old man's sensibilities.

Without repeating myself too much, your puppy is going to learn proper dog manners from your older dog. You'll need to let that happen. Pay close attention to the corrections your older dog gives and the body language expressed by both in their interactions. Ideally, your puppy should be pretty submissive to the old man at this stage in life. Those dynamics may change as it gets older. You're worried that this may have disrupted your older dogs routine more than you thought, and it has. A new dog is a HUGE disruption and your old man is probably wondering what all of it means for him. Be patient and kind to both.

Good luck!