Hello!
"rewrite and extend all existing articles of my website:" I would find it helpful in creating my bid to see the website or samples of the articles. And how many? Regardless, this form of copywriting is what I do – rewrite existing text to expand, to increase readability, and to add clarity and color or personality.
In fact, I can show you screenshots of the Before & After of a communique job I did like this today for a friend. In her case, the genre was professional/medical, and her goal was for the statement she had crafted to be more persuasive. But the genre, audience and objective doesn't matter; I will need to know, but I can handle virtually everything.
"native English speaker only:" I was born (in 1972) and raised in Michigan, United States – Midwest America, the heartland, home of Detroit, the automotive manufacturing headquarters of the world (at one time, anyway), and where Motown music was born. I am three hours from Detroit, and I am as Native English as you can get.
"experienced and expert writer:" I learned proofreading at a local newspaper and now have decades of editing experience. I launched my own editing, copywriting and publishing business, through which I am responsible for the pristine, polished look of 5 manuscripts that grace the virtual shelves of Amazon. I write and rewrite for a corporate nonprofit (whose director calls me her secret weapon) on a regular basis. In my own pursuits, I mostly write persuasive essays.
We should talk.