Biscuit puppy need help

Hello, my name is Biscuit, I am 4 months Golden Retriever from London. I was very happy and active but since last month everything has changed. I stopped eating and didn’t play. I wasn’t excited about walkies and the only things I wanted is cuddling a and sleeping. Vet took my blood test and it was very toxic. Vet said I have a shunt at my liver which doesn’t allow me to be active and grow. At 4 months my weight is just 9kg when healthy puppy should weight around 15-19kg. I need scan and special treatment (3500£). If it won’t help, I will probably need an emergency surgery (another 4500£). Otherwise I will not have a chance to grow up a healthy and happy doggo. Please help me to enjoy my health puppy time and become a big handsome guy
-Sir Biscuit and his parents