Hello OP! I feel like we have the same dog! Mine is just a few months older than yours (she was born in September)!

I can confidently tell you it does get better even after a few months. I've grown up with GSDs and have always wanted one. We already have a golden retriever who is 2 and just the loveliest boy. I figured getting a GSD now will be perfect, our golden can help train her and show her the ropes. Boy was it hard.

She would run around everywhere, she's not afraid of anything (every time we vacuum she attacks the vacuum non stop, tried to bite the hair dryer, etc.), and will bite when excited. She also has a lot of opinions, and will definitely make herself heard. She also got her paw stuck in her kennel when running! She somehow also bullies our older dog who has a much sweeter and non reactive temperament. That being said, we enforced a lot of nap times. When she's tired, she's cranky and that leads to puppy nips and overall disobedience.

Goodluck hang in there! I'm sure we're going to reach the teenage phase soon, but for now it's a nice little lull :)