Tl:dr: how do I teach a puppy not to jump on us? And tips for puppy proofing a large backyard. (1acre)

Long story short I ended up with a German shepherd. She is around 5 months old, I think. A family member couldn’t keep her, gave her to me because I have a big yard. She has been an outside dog. I have a small house and already one big dog. So I don’t have room for her inside right now. But I bring her inside at night and she sleeps in a crate. And she does very well in the crate.

I took her and got her all updated with shots, and new toys, and everything. She hasn’t had any training, so I’ve started trying to tech her to sit.

The problem is that she is tearing up my yard. She is chewing everything. I try to keep things picked up. But she chewed on the hoses to the pool pump. She chewed a cord and disconnected my gate battery (that was scary!) I didn’t consider how to puppy proof one acre of land. She has a bunch of toys but she chews everything, patio chairs, etc. I know she is teething right now. But how can I help make my yard more safe for her, and my things?

And the only other issue is that she jumped on my 5 year old and knocked her down once. And now My 5 year old is terrified of her. So I keep them separated. Is there a good way to introduce them so that they are both comfortable with each other?

How do I teach the puppy not to jump up on us??

I don’t leave my daughter unattended with any dogs but if the puppy is going to live here forever we need to figure out how to all live together happily.

I can’t afford professional training right now so I’ve been doing a lot of YouTube research. I’m just not familiar with German shepherds at all! So I could use some advice. Thank you!!