if you can afford a trainer and one is conveniently nearby I would highly recommend one. in my opinion GSD's excel with a job or purpose but for the average person what job can we give them? they learn sit, down and other simple tricks very easily. a trainer can better stimulate their brains in a productive way.
I moved to a new area so my guy has been away from a trainer for about 2 months and I'm now looking again! getting a little crazy
trainers here are so expensive and i cant afford it, i never had any prob with my two other dogs but when i got them they were 1 year old.and not as big as the gsd. i just continued the training my self, no leash walks they jump,heel, do tricks...but again never trained a puppy