None of the health statistics are a guarantee. Most of them say something like, the instance of cancer X is 2.45% higher in intact dogs than in speutered dogs, with a 5% p-value. The only statistic I do trust is that neutered dogs have a 100% less chance of getting testicular cancer and spayed bitches have a 100% less chance of getting ovarian cancer. Those two...I'll hop on board with, everything else has not been proven in any laboratory to actually CAUSE a cancer.
The majority of dogs in the United States are speutered. They live long, healthy lives. If one does come down with cancer, there is absolutely no way of proving that it was caused by an early spay or neuter.
In my opinion...if you're coming onto this forum, and asking a bunch of strangers for speutering advice, you're not ready to handle an intact animal. This isn't anything against OP, its against every single person that has done this over the last two years. Listen to your vet, or breeder, or other people you know and trust. At the end of the day, a normal pet owner (dog parker, not hardcore obedience trainer, ect) will have a much harder time with an intact animal. In my opinion, for most people, the joy of owning said dog will decrease by way more than that statistic about cancer x or cancer y.
It also takes away from the possibility of at 18 months someone with another GSD coming to that person and saying, "we have two beautiful dogs, they have amazing temperaments, we should breed them and make thousands of dollars." And the person with that dog actually thinking about it. I know we all hope that people wouldnt do that, but when you can get $500 a puppy or more, 10 puppies are a nice little paycheck for a few months of work and a little extra dog food.