I really wanna give my dog a good soup for his cold but is it advisable? pls help me out here..

I recently was gifted a saint Bernard by my frend, he's only 47 days old. the frend who gave me has left abroad Nd I couldn't talk to her about food, she had adviced me to feed him every four hours with royal canin starters. but wen I look at t I feel like I'm feeding him more for a day that too with curd each time, we had dogs before Nd mom used to take care of their food, now since tonight I feel like he has cold Nd running nose, I also was gifted with a 2 months old pom teddy but I'm aware of his diet as this frend guides me, but I'd really appreciate if someone helped me a diet chart for a large breed, the vet I consult doesn't seem to know much abt Scotch's diet. I wish I had friends who had saint Bernard too, I really wanna give him a good soup for his cold but is it advisable? pls help me out here..