aggression biting training

Hi, so I adopted a Doberman puppy at 8 weeks and he is now 14 weeks. When we got him, I realized he had a biting problem. Any time we tried to play with him or even just pet him, he would try to nibble/bite our hands and feet. We figured we would discipline him and he would get over the issue...

Hello. I have a nearly 4-year-old 57lb Doberman mix (fixed, mostly doberman, don't know what else he is mixed with..) that I rescued at the shelter in February. Since I've had him, he has progressively become more and more aggressive. He was returned to the shelter by other families 2 times. I...