Maxy’s behavioural lessons

Please help, or he will have to be rehomed again! Maxy is a rescue we adopted a few months ago. We fell in love with him instantly and had to bring him home to be best friends with our other 3 year old dog. Unfortunately his behaviour has progressively been getting worse over the last few weeks and he is really starting to become an issue. He barks constantly, he cannot play with our other dog without it turning violent, he does not listen and behaves like he is a naughty teenager. Other than this though he is a lovely little dog who loves his cuddles and walks that he never used to get. We understand that having a dog costs money and would willingly pay for his lessons however, he has already cost my savings in vets fees as sadly, within two days of us bringing him home, he was hit by a car and had to have major hip surgery. I hope that the dog lovers out there will understand my predicament and help me to create a safe, loving home for both my dogs.