Naturally, my most successful students are the most conscientious ones.
Becoming fluent from scratch takes anywhere from 9 to 12 months – if you lead a normal life with constraints: a full time job, family, friends, children, etc.
However, because you’ll be learning French in a natural way, you could be speaking fluently in as short as 6 months’ time, if you are catching up with French (for example if you learned at school but forgot most of it).
I don’t sell empty promises and I won’t tell you that you can get fluent in French in 3 months when you have professional and personal obligations. Unless that’s literally all you do, that’s just not going to happen.