Frank and Tanja are correct - you can't say "He has already said about this." The word "say" needs a direct object. You can't just "say," and you also can't say "about" something. You have to say *something.* For example, these sentences are okay: "He has already said A LOT about this." "He has already said EVERYTHING HE WANTED TO SAY about this." "He has already said A FEW THINGS about this." If you don't want to explain what he said, then you need to use a different verb, like "talk." In general: We talk ABOUT something. We say SOMETHING. (no "about")

“He has already said about this” is not proper English. In th US one would say either “he already talked about this,” or, better yet, “He already addressed this.”

Thank you.

"He has already talked about this" (more common in the US)= "He has already spoken about this."