Congratulations on your new dog! You didn't say how long he's been with you, but I can tell you that I usually give a new dog a month or even two to settle in and just relax and bond. Play with him and take him for walks, let him snuggle up next to you while reading or watching a movie. New people, new home, new routine, new diet, new noises, it's a lot to get used to and it takes time. When he seems ready though, I also recommend working on basic obedience. He may already know quite a bit at 1 year, or he may not, depends on his circumstances, but he should catch on pretty quickly. GSDs LOVE to learn new stuff. Just be patient and consistent, using lots of praise and treats, and it's very likely he'll be well behaved in no time.
My puppy, now 8 months old, was nearly 100% on recall on or off leash by 5 months - until she decided she didn't want to🤗. The first time she openly defied a recall I knew I had to somehow nip that issue in the bud. So I spoke with a trainer about the possibility of using an e-collar...I couldn't figure out how I could convince her to come when she was off-leash and at some distance away from me any other way. But the trainer gave me another option, and it worked beautifully! She said to leave a leash on the dog in the house. At random times, and especially when the dog is busy doing something else, call her. First in a normal voice once and once only. If the dog doesn't come, call her again in a more demanding tone, but again, use this tone once and only once. If the dog still doesn't come, walk over to her, grab the leash, and without a word quietly but forcefully drag the dog over to where you were when you called them. Once there, praise the dog profusely, then release her to go about her business again. Wait and watch for the dog to be distracted again, and repeat the recall process. She told me that even the most rebellious dogs get the picture that come is not an optional command within a week or two. For my puppy it took only two iterations. She has not failed to recall in even the most distracting of circumstances since, so I highly recommend this approach! Good luck, and again congratulations on getting the best dog breed on the planet!
It's not the size of the dog in the fight, it's the size of the fight in the dog. Mark Twain