I've had many foster dogs and my own rehomes that had food aggression and turned them around it's not a quick thing to sort it takes time. Look at nothing in life is free method training that what I used I used to make them work for all there food, toys, walks etc. Feed separate to start with never leave food, toys etc down to start with. I would look at doing more meet and greets with them both if possible. Also be prepared for a few tiffs no dog comes into a home and is perfect