My 5 month old German Shepherd likes my 8 pound Yorkipoo but he’s too rough with her. How do I introduce them?

I'd use an expen and get them used to each other that way. We cover how we raise our GSD and Malinois puppies in our home in the video 8 weeks to 12 months. Besides Mals and GSDs we also have a 6 lb Shih Tzu and a 15 lb Border Terrier so I'm familiar with what you are going through. I have a 6-month-old German Shepherd right now and he's only allowed to interact with the small dogs while he's in an ex-pen or on leash. Leashed walks together are good too. Until you have obedience control of the puppy I'd manage all the interactions with a leash or barrier. My ultimate goal is always for my dogs to get along but not be overly fixated on each other. I would prefer they like hanging out with me more than the other dogs and at the very least that I am able to call them away from each other so until I have a great relationship and obedience foundation with the younger dog I manage all interactions.