"but I have many times talked with people who hope to learn French to fluency in six months, and people who are convinced they could never learn it no matter wh

"but I have many times talked with people who hope to learn French to fluency in six months, and people who are convinced they could never learn it no matter what." It is a question of intensity. If all you do is speaking french and learning grammar and are surrounded by french people, you could reach some level of fluency in 6 months. But not while learning it on the side (unless you are very talented).