Hello! I just adopted a 6yo German Shepherd from my sister. We have had her for 3 days. She is agressive when people come to the door and I want to train her not to be. My question is: how long should I wait to start obedience training with her? I wanted to give her enough time to get used to our family and get used to her surroundings because I know she's probably a little scared and confused by the change in her environment. I also would like to start taking her for walks but I know she is also agressive with other dogs. Should I start training her for that also or give her more time to get used to the new yard?
And last but not least, is it more difficult to train agression out of a dog that is as old as she is?
Thank you.