Sweetness of temperament is the hallmark of the Newfoundland; this is the most important single characteristic of the breed. They are nicknamed the “Gentle Giant” and “Nature’s babysitter.” They are protective of children. The dog Nana in James M. Barrie’s Peter Pan was a Newfoundland.
Relative to other breeds, Newfoundland puppies, especially older puppies, tend to be calm. Newfoundlands take up to three years to reach full maturity. They have deep barks, but are not good guard dogs. They have been known to grieve when separated from their families. Their large size makes them difficult to keep in many living situations.
and about healt issue, There are several health problems associated with Newfoundlands. Newfoundlands are prone to Hip dysplasia (a malformed ball and socket in the hip joint), Elbow dysplasia, sub-aortic stenosis (a heart condition) and cystinuria (a hereditary defect that forms calculi stones in the bladder).