This looks like the result of terrible breeding to me. Now, you are not in the US, so I don't know how things are where you are. but because of the AKC stupid "standards" for how German shepherds "should" look people here breed dogs to have those deformities on purpose, and this is what they have done to German shepherds. If this is the case with your dog, and he was bred that way on purpose, there won't be anything you can do to correct it.
If his parents and littermates don't look like that, then he has serious hip dysplasia. There are no cures for this, although there are medications that can ease the pain, and as young as your dog is they may be able to treat him to keep it from getting worse. Untreated, it will lead to osteoarthritis and shorten the dog's life as well as making it less enjoyable for the dog.
Give him a soft bed, don't expect him to climb stairs, use ramps if possible, don't expect him to run, and get him to a vet as soon as you can for X-rays and treatment.