How to change div content before page load (Chrome Extension)?

Question

JavaScript

How can a chrome extension change the content of a page before it loads?
I need to change

<div> просто </div>

on the

<div> непросто </div>

at the same time, that "simply" would not appear at all. So far, using content_script, I can do it, but the initial word changes within 3-4 seconds. Please tell me how to fix it.
PS "run_at": "document_start" using