why dogs cry during night or they sing song ?

If they are crying while they are asleep, they are just dreaming. Dogs do dream and sometimes they cry or growl or bark or moan during the dreams. If they wake up in the middle of the night and start crying, they might have to go to the bathroom. They also may have heard something outside and its just natural instinct to warn their owner that they heard something.

Its winter , they try to call the mate ( i guess )

SOme old people use to say that dogs see devils and demons and when they see they start making different noises to warn other dogs or other people.

All dogs do that especially when puppies sometimes they are lonely and sometimes they just want attention.