Ok so recently my dog(I don't know if this matters but she's a German Shepherd) has been chewing everything outside which I'd presume because she's teething but she is 6 months and I don't know how long teething will last in dogs. So what's a way to train her not to chew or play with things I don't want her to play with. I on the other hand got tired of it and is tied up in the backyard due to school meaning I'm chaining her to a small area outside close to her house, food, and water is this a good idea? I feel like it's not, but on the other hand I feel it's needed she's been doing it for months and told her and showed her once a day not to play with something which has been effective, but recently went back to playing with things I told her not to.
Chaining a dog is not good in general and might increase the problem in this case.
Your dog is young and full of energy. If she's bored, she entertains herself by chewing on things. Playing with her and taking long walks is a better way to entertain her. With some training, you could ride a bike or skateboard or roller skates and have your dog run with you.
Most young dogs prefer to chew on things that smell, especially shoes or leather products. Offering her a toy like a rope or hard chewing bones may satisfy her need to chew on things without destroying your stuff. But it's totally normal for young dogs to chew on things. They don't have hands to feel objects, so they take them into their mouth and chew on them.
Now to the discipline.
You must discipline a dog within 3 seconds of doing something wrong. When you come home, show her a chewed-on object and scold her, she won't even kow what you mean. She cannot understand why you are showing her the object and are so angry. She cannot understand that the chewing she did an hour ago makes you angry now.
If you don't want her to chew on things, you should put those things in a place where she cannot reach them. You should entertain her by playing with her or taking walks, then she won't be so bored anymore. Putting her on a short chain is even more boring and could make the problem even bigger.
Whenever she does chew on things, have a small and somewhat harmless water spray bottle. Limit their dependability and give slight discipline. Buy a lot of chew toys too! Dogs have a lot of habits like this when they are a puppy. Chewing things for puppies can sometimes be uncontrolled, for I had the same problem with my schnauzer. Avoid products that have toxic ink or ingredients towards dogs, especially plastic food bowls!
Buy a couple of butcher bones and after meals give the pup a bone to chew on for awhile - Maybe half hour to hour. Then their jaw will be too tired to chew on anything else! Instead of buying new bones all the time, refill the empty butcher bone, I used high quality chicken strips, softened 5 seconds in microwave and cut in three then stuffed in there so they are hard to get out. Assuming your dog is a puppy, this is a normal phase you can help them get through while not chewing up your stuff. I did it from about 7 months to about 14 months. Also crated him when we went out, with the bone to chew, very happy dog, and owners!