Q1: Are you the OG author of this novel?
A1: No, nor do I claim to be.
Q2: Then isn't what you're doing considered plagiarism?
A2: The original author is credited on this novel's homepage; so legally speaking, no it's not.
Q3: Since you're improving the grammar of the novel; does that mean there won't be any errors?
A3: I try my best to proofread a chapter before I post it, but I can't guarantee that you won't find a miss-used word tense or misspelled word every once in a while.
Q4: Where can I find the original novel?
A4: https://www.webnovel.com/book/transmigrated-as-side-character-i-will-steal-all-the-heroines_20503282606112005