I would say an English mastiff is an ok first dog. They are pretty laid back. But not all mastiffs are equal, so I wouldn’t recommend a Neapolitan, Cane Corso, Presa Canario.. those wouldn’t be a good choice until you’ve experienced not only owning a dog, but owning a massive sized dog, and a challenging dog. It can be hard just dealing with their size, let alone their tendency to seem “stubborn.”