I have never had a French class in my life apart from first year in secondary school, and started from zero a few years ago. Started off just doing a bit if Duolingo but didn't get anywhere until I went David Goggins on it. I'm not a big fan of the French themselves but they possess the most gorgeous language on the planet, I got obsessed with learning it. Going to do a C1 before the summer, see how I get on.

So, if you are determined and willing to sacrifice an hour a day and be organised, you absolutely do not need classes.