Do you have to use the continuous present with "still"?
Commonly you would indeed use the continuous present. For example:
He is writing. He is still writing...
He went for a walk. He is still walking.
However, the continuous present is not required. Consider:
He has been a famous writer for many years. In fact, he still writes.
That's the simple present, used with "still".
Let's consider your example sentences:
I still reading the article
I still reviewing the article
These are not correct, because present continuous should be "am reading" and "am reviewing".
I am still reading the article
I am still reviewing the article
And this sentence...
I still review the article
...reveals an interesting property of the word "review". If you are reviewing an article, it should be present continuous. "I am reviewing the article". In the simple present, it means "in general" rather than specific. "I review articles" "I still review articles". That means "many articles, in general". But this is going off on a tangent about how the word "review" works, rather than the word "still".