Teach small puppy/dog to walk on a leash

She’s pretty good at stopping when I say stop and sitting down until I say let’s go but after that she tries to run ahead a bit more than I would like her to. I have back problems and she’s a smaller dog so it’s hard to guide her with the treat directly in front of her nose (so she knows to stay at my speed and not pull) Any tips on what I can do?

Breed: mini schnauzer Age 3 months