I don't think I taught heel at 4 months of age, even with my latest puppy.
What I found worked for pulling on walks with both him and Mic was stopping when they pull. You can wait for them to loosen the leash before you continue the walk, which didn't work at all with Mic, but does with the puppy, or you can wait until they look at you, and then praise or use a bridge word and give them a treat, which worked great with Mic.
What I found worked for pulling on walks with both him and Mic was stopping when they pull. You can wait for them to loosen the leash before you continue the walk, which didn't work at all with Mic, but does with the puppy, or you can wait until they look at you, and then praise or use a bridge word and give them a treat, which worked great with Mic.