Honestly I don't see any GSD in that dog. Mainly Great Dane and he could possibly be a Malinois mix which are A LOT A LOT of dog and not for the faint of heart.

Will he be your first dog? Behavior issues can come up in any dog, regardless of breed. Just get him into obdience classes right away, he probably has a lot of energy and you just have to be prepared to meet his needs.

Information on Malinois.
http://en.wikipedia.org/wiki/Belgian..._Dog_(Malinois)