@FJleert here is definition about needn't and don't need to

"You needn't listen to him" = It is unnecessary to listen to that man. If you want to listen that is your choice, but it's not important.

"You don't need to listen to him" = It is not necessary to listen to that man. If you do you will only be wasting your time.

I know I shouldn't have used "gotta" in a test. It's not a mistake I made because I'm a non native speaker. On the contrary, the usage of this word reflects that I'm confortable with using English in daily conversation. Correction is not an easy job because I have to correct an entry grammatically without changing its content. Like the example you demonstrated is where I made a mistake because the sentence was too complicating. I shouldn't have corrected that sentence like that. I just don't understand why are mistakes made by native speakers understandable while mine are huge mistakes that would take my marks off if I was taking a test? Apparently, I won't write "gotta" instead of "got to" if it is a test

@Mumtaz excellent correction given by a few individuals doesn't indicate that correction of all native speakers are as excellent as that of the individuals. Teachers are expected to teach people with high quality teaching skill of the certain language because they have high education on teaching the language. Why do you assume that correction of non native speakers must be inferior than that of native speakers? Language isn't science because there is no "perfect" answer. We have many different ways to express ourselves. People are able to decide whether the correction is right or wrong. Showing some respect to people who try to help regardless of who they are.

@Murillo Costa yea, you see the issue, eh? I'm not discussing whether correction given by a native speaker is right or wrong, but I'm trying to say that it's a wrong belief that correction given by a non native speaker is useless and must come with full of mistakes. We should respect people's work no matter what language is their native language.

@Murillo Costa sorry Murillo, don't take my comment personally

@Mohamed yes, that's what I'm trying to say. I'm living in Canada and have met a bunch of English native speakers. Some of them don't even pass a grammar test with a level I got. I know I make mistakes sometimes, but it doesn't mean that I shouldn't correct entries of other non native speakers. A non Chinese learner may know more about Chinese grammar than I do, believe or not. Correction of the non native speakers are even better than that of native speakers in terms of grammar

@Learner SC well, I will write a post for correction in the notebook area next time. Thank you for your advice

@Mumtaz  I can tell you that they have to wait for a teacher teaching the language they are studying to answer their questions. The teachers are qualified to teach people with the certain language, and their answers are supposed to be correct and reliable. However, I don't think non native speakers who have been studying the certain language for years are not able to correct other non native speakers' entries. It's just a bias to assume that the corrections given by the non native speakers must be wrong based on some kinds of perception

@Camilo  Unfortunately, u can't even have a correction answer from native speakers sometimes. For example, some English native speakers will write "your" instead of "you are", which not even a person learning English at beginning level will make. Another example is misuse of coordinate conjunctions such as "and" "but" "or" and "so" that are put in a sentence without a comma in front of them. THEY ARE ONLY USED TO CONNECT TWO INDEPENDENT SENTENCES. Unfortunately, some native speakers are not even aware of their mistakes.