
Provided you bought from an experienced, reputable breeder, THAT'S who you should be taking your advice from at least while your puppy is still within the growth period. Yes, you could go raw, but you'd have to know what you are doing so your puppy receives a properly balanced died, as fits a dog of his breed and age. And that's where, for me at least, buying a good quality complete puppy food is generally speaking, best. GSDs can have sensitive digestive systems which is why I favour the breeder over anybody else. She's most likely to know what suits her bloodline as well as breed. Good breeders would have given you a diet sheet and a small supply of the appropriate food so you don't need to switch, risking upsetting his digestion.
I go for a food that lists meat, or fish, as the first and so main ingredient. And for me, a protein level of no more lthan 26% is probably best too so you don't force too much growth (bone development), too fast. And having found one that works, stick to it - if you keep switching, again you risk digestive problems.