One of the greatest mistakes I ever made was getting a buddy for my dog. I am new here and I am sure you will get much better advice but mine is ... dogs are like people set up on blind dates in some ways ... they don't always like the other person. Unfortunately they don't have the option of saying they are ill or work called and escape.
Also, sometimes a GSD might like a smaller breed ... and not be all that fond of another GSD. Some of the best advice I ever got was a dog doesn't need another dog to keep it company .. it just needs a pack leader. Just sayin'
Again, I am new so please don't take my words as gospel ... just my experience .. I never mix my dogs until they had a chance to meet and greet and let me know what the heck I was in for. Sometimes I ran for the woods.
Best of luck. Maggie