We bought a great dane puppy at 11.5 weeks old from a breeder after recommendations that they are gentle, quiet and easy to train. They are lazy and good in apartments so we thought it would be the perfect dog for us. It has become obvious that the breeder did no training with her and I would be surprised if she had ever been given boundaries. She grew up with 3 adult danes and another pup from her litter in the laundry of the breeders house and was allowed to roam freely in the backyard all day while the breeder was at work. She had never had a leash on or been toilet trained either and she is perfectly comfortable to pee next to her bed or even lay on a pad where she has peed which is unnatural to them if they have been brought up right. The breeder said to me that she had started puppy school and training with the other pup and she intended to keep her but nothing with mine as that was my job. She is not treat or toy motivated and doesn't even eat her food for hours after it has been put down so training her out of bad behaviour and directing her towards good behaviour is difficult. After 5 days of having her and introducing her to boundaries like not being allowed on the couch to walking her on a leash she has progressed from barking aggressively in response to full on biting. She is also abnormally aggressive with her toys and growls randomly for no reason. My partner and I have grown up with dogs and have been firm but not harsh with her and she gets plenty of exercise and doesn't destroy the house or whimper when we're at work and is fine sleeping on her own so separation anxiety isn't an issue, nor is food aggression. She has also taken to attempting to destroy anything I touch once I put it down (like books, phones, computer mouse, cushions). I have heard that rarely you will come across a dane that is just naturally aggressive and it is very hard to break them out of it. I am concerned that because we both work we don't have the ability to put in the intense training she may need to break these bad habits and learn correct behaviour. Should I take her back to the breeder or attempt to fix the behaviour despite not being able to commit 100% of the time due to work?