my puppy can't be alone even for a second he starts whining what to do?

This called separation anxiety. It is very common in dogs specially in young pups. You can give him plush toys, chewy toys ,interactive toys which are available in market to keep him engaged and provide mental stimulation to him. In that way he won't be bored and would not suffer from separation anxiety. You can also start training sessions for him with trainers available on Kuddle itself.