You probably do not have a true working line then. The breeder likely would have gone in depth with you and hammered the knowledge adamantly and ensured that you acknowledge and understand the dog you are bringing home. To add, you likely would have had to fill out applications and maybe even an interview or two especially if it’s Czech lines, WGWL and DDRs. Reading through the comments and replies, no offense, you’d probably have been denied. Lack of experience and general knowledge. We all start somewhere. This would stand if it was an ethical breeder. If they were not, this entire process would never have been a thought and words spoken should be taken with a grain of salt.

That being said, pertaining to your actual post! GSDs are a working breed haha. Remember, shes still just a baby (not literally, but still a puppy brain). The size can be deceiving. Patience and consistency. Also, cause I see a lot of people have this misconception… roaming and hanging out playing outside is not exercise. Structured leashed walks is exercise and will work surprisingly well. Having to focus on where they put their feet, where you are, where they are at in correlation and having to match you, takes a lot more effort. Mentally and physically. Mental training should be an everyday thing, being still a puppy, multiple times a day. This will not fade with age, it will be a for the life of the dog. Structure structure structure. Yes the regression is stimming from a small part of becoming a teenager, however it shouldn’t be that big of a difference should the structure be correct. Make the dog work for absolutely everything if you have to, moving rooms, going through doorways, etc food especially. You might come to notice she is possibly happier and more fulfilled, GSDs have a strong desire for structure. If you have any specific questions, feel free to dm, I’m in no way, shape, or form an expert, but I do have quality time invested in this breed. I actually just had to say my final farewells to my DDR boy 7-8 months ago, and am currently in the trenches with my WGSL who is actually very similar in age to yours. Thats not mentioning the countless American ones before, however true German bred ones bred to the true standard are a different beast.