Hi and welcome to DTA. You'll find loads of info here and if you can't find what you are looking for, just ask

that all is very helpful knowledge! I'm so glad I can come here for my own training and positive reinforcement

Your girl sounds great! There are solid black german shepherds, but it is more common in the long haired type.
Please put up some pics of her in the Meet the dogs section. We all love to see pics of dogs

You say she doesn't like it when it's dark? Well, that may be because she was a stray and she is at a stage in her life where a lot of things are scary. Through tricks training and obedience you can build up her confidence. Also she has only been with you for a couple of weeks, so she is still learning to trust you. That is something that might take a while.
A tip on teachnig her which toys she can play with. Every time she takes a toy that is not hers, trade her with a toy that ís hers and play with her. Be consistent with that and she will learn. Teaching her to drop on cue is a good thing, here.
The jumping and nipping is a puppy thing mixed with a little herding. When she nippes at your hand, don't pull your hand out of the way. I know that is the first reaction, but she might turn that into a game. If you don't respond to it, it is no fun, so the behavior will fade. Reward the moments that she walks besides you without nipping and jumping.
If she is really jumping into you, stop and stand still, totally ignore her. When she has all four on the floor, reward.
I don't know why she is jumping, but if it is excitement, it is important you stay calm. Don't talk in a high pitched tone. High pitched voices can overexcite a dog sometimes. But give her a chance to get the energy out. So walk a bit and if she is good, do a little game of tug. That way you can redirect her energy into a toy and a game and she will learn that being calm gets her a game or reward.