I have trained several dogs and my latest (a one year old Shitzu/Maltese which I got at 8 weeks was the hardest to train out of all my dogs. I would say my pup wasn’t fully trained for a full 5 or 6 months. And I was home with the dog every day and when I was home I took her out every 15 min. One of the training methods I particularly like (although didn’t work with her) is putting a bell by the door you take the dog out to and every time you take the dog out, you say “wanna go pee pee or out?” And then ring the bell and immediately take the dog out, once the dog does his duty outside, reward immediately. My dog will only go to the door, would not ring the bell, all my other dogs picked it up without any issues imediately. I also crate trained my puppy from day one and she still goes into the crate at night to sleep. During the day when I go out she is trustworthy to be with my other dog in a confined area. Patience, consistency and rewards are the only way the dog is going to be successful.