Something that is ordinary or common can also be called plain, a homophone for that word would be plane. Similarly, something that is to see how heavy something is, would be to weigh, a homophone for that word being way.
Training your dog.
It is very important to train your dog. It keeps your dog's mind active, and it >help(s)< to build an understanding between you and your dog. Often owners will shout at their dogs or even punish them ,when what is needed is training.
There is an error with sentence 2 , and you would change help to helps
They shouldn't be bad for the ocean they are part of it.The only bad part is that they sting and they take up some big parts of the ocean.