Is it normal for a 9 week old puppy to sleep this much?

We just brought home our golden retriever puppy 3 days ago and shes sleeping like 18-20 hours a day. I know puppies sleep a lot but this seems like a lot even for a puppy? She wakes up, eats, plays like crazy for 20-30 minutes, then crashes again.

The breeder said this is totally normal but i keep watching her breathe to make sure shes okay lol. She seems happy and healthy when shes awake, eating well, no weird symptoms.

First time puppy owner over here. Is this actually normal or should i be concerned?