
What do you mean overbred? It is a concept often levelled by non ddog people to mean inbred. Inbreeding of itself does not create a problem dog, as all it does is bring out what is there. If you mate two related animals together you have a higher chance of their traits being exhibited bythe offspring when their genes combine, than if they were totally unrelated, as they will both carry more of the same genes.
In knowledgeable hands this can be a great tool for weeding out unwanted traits and fixing desired ones, and it's main negative effect longterm if overdone is reduced fertility and vigour (here we are talking very close breedig for generation after generation which is only practiced in lab animals, and would only occur to a lesser extent in breeds with very small gene pools, where there are very few founder animals in the breed.
You say the pup was locally bred. Was this a respected person in the canine community who kept their dogs for show, and breeding was the by product. If not it could be that your pups ancestors were the result of two poorly bred parents descended from exports from UK?US?European Puppy farmers. Good breeders over here will rarely export Asian countries as the Welfare laws and standards are often poor.
This doesn't of course help you. As a breed they are quite exciteable and you will need to teach the pup to be calmer.
Never shout or move quickly around the pup, as this will excite it more. Speak in a low and slow voice. Also pet him with slow steady strokes that will have a calming effect. When it gets excited at the sight of something, turn it away to break eye contact, and speak in a calm but firm voice.
Wyhat are you feeding? Avoid foods with coularants and artificaial preservatives, and too much Protein. If it is Puppy food, avoid anything over about 28% Like with hyper children dogs can react to these additives in their food.
Take the pup to a good training class.