21 week old puppy struggling with walks!!!! Have had her since 9 weeks old

hi!

my puppy got fully vaccinated this month (YIPPIE!!!) and we have been going potty outside! minimal accidents inside, luckily its only been pee accidents! shes done so so so good with going outside and waiting until its time to go (we go at 7am, noonish, 4:30pm, 9pm) and i try to make one of those a longish walk, usually the 7am one!

she struggles BADLY with keeping up on walks, wanting to smell absolutely every single speck on the ground. be it car oil, bird poop, literally everything and 85-90% of the time i WILL let her smell it, shes a curious girl!! but the other 10-15% of the time i literally have to DRAG (not literally i just pull the leash so she will come, she wears a harness. i also will just tap her or give her a pet to get her attention again) her to continue the walk or to come up the stairs. once she finally does end up coming i reward her with a treat or give her some kind of good girl yay or something along those lines. What do i do? Do they grow out of this with age? I know shes SO young and im not trying to expect her to be fully trained (we start training classes this week so hopefully i can learn valuable skills and lessons) im proud of her and her accomplishments shes truly been a breeze and a walk in the park for a first puppy, i really got lucky.

i hope this is just a phase she will grow out of. Shes not VERY well socialized, i had a puppy before her for a few days who died of parvo (the puppy had it when i adopted her) and it made me terrified of taking my new puppy out on walks and she was growing FAST so carrying her everywhere was getting… heavy. She jumps up to everyone (something were working on) and gets excited every time someone passes by or even a car on the street or a crow in the tree and even a leaf rolling in the wind, the girl has to investigate!
im really excited for the puppy class and know it will bring some clarity and general advice, i just thought i would ask here as well before the class so i can start working on the issue 🙂