[New dog] are our dogs playing or fighting?

We got a dog about 8-9 months ago and he’s a yorkie but we decided to get another dog just a few weeks ago and she’s a bigger dog than our older one and because she’s still a puppy her teeth’s are still growing and their very sharp.

They pause, and they also take turns but the thing is our smaller dog gets bruises. I don’t know if it’s because their “playing” is actually them fighting or because our bigger dog’s teeth’s are sharp and accidentally gives our smaller dog bruises while playing.

I make sure to stop them when I hear any loud barking and growling but I’ve seen some dog play videos and the barking and growling seemed normal for play. But our bigger dog sometimes bites in the ends of our smaller dog’s tail and drag her (which we make sure to stop them before she actually drags her) but is that a normal play too?

We’re getting her into a trainer soon and I’m planning to ask them but I’m very anxious and can’t wait