My dog needs surgery for her leg or we cant keep

Hi my name is Lucien I am a teenage boy (14 yo) who is trying to help my 2 yo dog whos named Nala she is an adult pitbull who has been injured with a fully torn ACL which causes her pain and demobilizes her. we only have enough money to pay for a small amount of the surgery with us still needing around 3500 dollars to pay for it. with the total cost being 4500. It's either that or we have to put her down. As she is my first ever pet and she is such a sweet girl I was devastated when hearing this and couldn't keep calm for the rest of the day. Even now I shake while typing. Any help, Please!!! I can get the vet statement from my mom (Erica) if any one needs any proof.