My Dog’s Anti-Aggression Education

Hello dog and animal lovers. I am starting this campaign for my dog Shark, who is an American Staffordshire Terrier. He is a blue staff and has been some trouble since he was a little pup. I have put him through personal and professional education, but he still has problems and I have been trying and trying to fix his bad behaviour and never gave up. I am still trying, he is a lovely dog but he is being very aggressive towards other dogs, stranger ones and even friendly ones. We are trying to socialize him more with different dogs but as soon as we let him free he doesn't listen to anyone. I have been told by the vets we need to make a castration, because he is also aggressive towards female dogs, so that we can calm him down and he can go through another education program with a professional trainer to fix his aggressive behaviour. Sadly, I have spent so much money on him, that I am just not capable of spending anymore, and sadly professional help costs money in our situation. Both the castration and the education cost around 500 euro which is just impossible for me and that is why I came here, to ask for little help if possible. I hope you all understand that is something my dog needs for his and my own happiness, I have talked and consulted with different doctors and specialists and we think that is the best solution. Thank you for the attention!