Here are a couple of issues that might mean that your puppy needs significant training.
They're already showing signs of aggression towards other dogs
If despite being very young, your puppy is showing signs of aggression towards other dogs, then you must quickly find a suitable training class. Whilst their teeth are small and not very sharp, and they themselves are small and weak, you might find it amusing or endearing when they leap at other dogs and bite them. Unfortunately, this behaviour will quickly become troublesome if you don't eliminate it.
For example, if you let this behaviour continue, it will make future experiences in the vet's waiting room frightening, as your dog may injure the other animals that are in this space. Likewise, you'll find it impossible to walk them through busy dog parks without them causing a scene and will be unable to use dog-grooming services when there are other dogs on the premises.
Working with a puppy-trainer will enable you to determine what's making your puppy aggressive. For example, their aggression might be caused by jealously or anxiety. Once you find out the cause, focus on activities that teach your puppy to behave differently when their anxiety or jealously is triggered. With this obstacle out of the way, you can then start perfecting their socialisation skills so that the above-mentioned situations don't cause either of you too much stress.
Their vet visits have been disastrous
If your puppy's previous vet visits have been difficult, then they probably need to be trained by a puppy-trainer. For example, perhaps they had an accident in the waiting room but became so terrified that the vet could not examine them. If things like this happen, the trainer will help you to work on house-training them. They will also teach you how to keep your puppy calm when they start to get overstimulated or frightened.
The trainer may also discuss the things you're doing that are worsening your pet's behaviour. For example, this includes if you raise your voice when your puppy is already hyper and over-excited, as this can add to their excessively-high energy level. Conversely, if you often use a soft, gentle voice when your puppy is fairly calm but is doing something bad, the trainer might inform you that you need to stop this and start using a more assertive tone. This way, your pet understands that you are the dominant one that they need to listen to.
Contact a service for more information about puppy training.