AFAIR I finished the French Duolingo tree in something like four months as well. I did practice every day with some dedication (preparing for a move to France),

AFAIR I finished the French Duolingo tree in something like four months as well. I did practice every day with some dedication (preparing for a move to France), but I don't think it was more than an hour per day on average. I did have experience learning other (non-Romance) languages before, and I think that helps.