I speak Italian decently (not great) because I studied it for four years in College. I can read a bit of French because of the large number of overlap between it and Italian and English. However, it's a complicated language, to say the least. I don't think it's possible to learn it without formally being taught.
In my opinion, the most important thing is dedication. You have to be willing to study and practice several times a week. Immersion can be helpful, but only after you've already mastered the basics of the language.