I don't think glueing your dog's ears without professional help or guidance will be of much use... I personally do not have experience with this, but my next door neighbour has a GSD that has one ear permanently down. I personally think it's because there was not enough of a calcium : phosphorous balance in the diet during growth, as their dog is exceptionally large for a GSD (they're bred to be 100+lbs). There's a lot of threads on here about how to help ears stand naturally without using glue, and those may be worth looking into. But if you have never glued ears before, I would consult a vet or breeder who has experience with it.