New dog owner has questions about German Shepherd

I have not gotten a German shepherds yet but I would like a German Shepherd and I have a couple questions first of all I would like to trade my dog to respond to a whistle and then a command so first I blow the whistle and then I give the command the dog will not respond to the command unless I blow the whistle first second I would like the dog to come to me if I blow the whistle and have no command to give third I want the dog to be able to play fetch so how can I achieve these things and also how loyal are these German Shepherd dogs and how do I make them super loyal (disclaimer I am a cat person but I want a dog that can protect me and play with me and walk with me) is it possible to train the dog to do any of these things thank you