The difference between stopping doing something and stopping doing something is not only a fixed phrases, but also a tense in grammar. When you say change, you should refer to parts of speech (names, verbs, etc. ), as well as past tense and past participle, are generally listed at the end of your textbook. The general past tense ends with ed, but the special one depends on rote memorization. The third person also has different uses. Verb +s, countable noun, after uncountable, just find a grammar book.

Grammar is absolutely important in the exam, except what the sentence is made of (in fact, it doesn't matter if you don't know it after reading too much, unless you need it in the exam). So, I think the most important thing is all kinds of tenses. In view of your poor English, you can master the most basic tenses (past tense, present tense and future tense). It is easy to remember that the past tense is a thing of the past, verbs end in ed, or be verbs become was, what has becomes had, and so on. The present tense is now, don't change it. The future tense, of course, will happen later. Will is usually used, and I think it is that I will go to school. I'm going to school.

Then learn more tenses on this basis. That's all that matters.

College English is not that I don't study grammar and word changes, but that I have studied it in middle school for six years. You said to study for the exam, but you can't use it. Of course, you can't study for the exam. First of all, how to pass the listening test? What about writing and reading comprehension? In fact, foundation and application are inseparable. There is no exam that only tests grammar. If you come up with a sentence, you can correct it, otherwise it will be a fill-in-the-blank question and a reading question. As a matter of fact, China used to teach students good English writing skills, but poor oral English, and some people even can't speak it well or at all. In fact, English learned in middle school is the same as that learned in university, and the ultimate goal is to apply it.

It seems that you are in college now, won't you take CET-4 in the future?

You said those words have no usage or anything, but they are already in grammar. In fact, Chinese also has its grammar. Didn't you learn it in elementary school? If you look carefully at the signs behind those words, such as n (noun), v (verb), ad (adjective) and so on, you will know what a sentence is made of and naturally understand the usage. In fact, all these have something in common with Chinese. Just like typing, you are the subject, typing is a verb, and words are nouns. If you add that you are typing, it means that you are typing now (present tense)

In short, just read more grammar books.