First of all, welcome, second of all, would love to see some pics of your German Shepherd and third of all, I learned a lot from this website. It helped me select the food I thought would be best for my dog, and taught me a lot about ingredients.
Royal Canin is not such a great food and it is no wonder that he doesn't like.
See iif you can find something that would be good, and available in Dubai, on this website.
Best Dog Foods