my puppy bad behaviour

Question
my puppy now is 9 month. Golden retriever, weight 26kg, male. he loves to bite people, but only play, not serious bite, but hurt. he loves to play ball and foot ball, how to make him little bit calm if meeting people or children? i hired a dog trainer for him, but it not work well, because the trainer said my puppy is little bit lazy. how to solve this problem? and is this ok, my dog was very naughty. sometimes i need to feed him by hand, because he often waste his food. he loves to tease me by doing naughty things.

thank you.

Answer
Hi, dont encourage your puppy to bite even if it doesnt hurt. He will think its okay later when he grows up. Then it will hurt. So everytime he bites, close his mouth and say "No biting". BE CONSISTENT, dont do it once and allow it the next time. And also change your trainer. If she cant train a dog not to go crazy with new people, she is not that experienced. My dog goes crazy when seeing new people too. If you let him jump on people, he will pretty much tackle them when he is 70lbs!