What can my 4 year old golden retriever eat?

My dog is a golden retriever and he has been vomiting yellow foamy liquid and he seems really sad and doesnt play anymore as used to. He won't eat anything only sometimes. I would like for someone to please put a healthy meal planner or a list of food or meals we could make for him at home because he seems to be getting better and eating a little more and I dont really trust pet food from the pet stores anymore. Also can someone tell me why he has been like this? THANK you!