Welcome, 6 weeks is really to early to bring a pup home. 8 weeks with his litter is recommended. Pups learn a lot from their mom, and littermates in those 2 weeks. German Shepherds are known to "landsharks". There are a lot of threads on best ways to raise and train your puppy. You can use the search engine or look under the puppy section for a lot of answers and ideas. Hope all goes well, and please share pictures. We all love puppy pictures.
The mom usually begins teaching bite inhibition, one of the many good reasons to leave the pup with mom at least until 8 weeks old. Since your pup was brought home much too early you may struggle with him biting you harder and more often than what is typically seen with older pups, and shepherd pups are known for being landsharks as it is. At 6 weeks old your pup is a tiny baby, I wouldn't put too many expectations on him right now... let him get used to being away from mom and siblings and bond with you.Keep things low key for a while so he can adjust. In the mean time you can read up on the concepts of NILIF and how to shape behaviors.
I highly recommend Kong toys! They are pretty much invinsible. Whenever he bites you, give a stern "no" and redirect his chewing to his chew toy. If you are consistent, he will soon learn to chew on his toys, not you arms!