Is is a crime or a plagiarism if you know that your english is not very good. You write a long arricle and give it to another person to correct the english in the article for you before you will now post it in the group or forum.
If you are sure that you didn't cite or get quote from some certain articles or other sources no that is not a crime.
It may belong to be the proof-reading and also editing.
But, what's for your article is?
If you are only going t use it as a post thread in this forum, you may not need to do such proof-reading and editing from expert, because once you are uttering it for sure, people are here to understand. And as what other members here say, you can use Grammarly to help you.
But, if you are going to use the article to be posted and more readably, unique, human friendly, and also sometimes SEO friendly, yes, you may need proof-reading and editing. This will help you much and you are not plagiarism on it.
And to ensure whether you are plagiarism or not, you are better to use some plagiarism checker tool, you can find them in some providers, bot free and also paid.