I am quite lucky to have been able to pick up French, English and Ukrainian as a child because of where I lived (and my parents always sending me to the local public school).
Throughout most of my school years (kindergarten to the end of high school) I usually picked either French or English as my main foreign language, depending on where I lived. It was a sure way to get a decent grade with relatively little work although grammar is no joke, no matter when or where you’re studying. I also attended Spanish and Russian classes because of requirements for the baccalauréat exam (two mandatory foreign language classes for a “bac S” and a third foreign language will get you extra points). In engineering school (in France) I continued with English but switched from Spanish to German as my second foreign language on a whim. In hindsight it was actually quite a good move because knowing a bit of German helped me during my first months in Finland, as written Swedish does resemble German somewhat (at least a lot more than written Finnish) and all food packaging in Finland must contain both a Finnish and Swedish description/list of ingredients.
For Finnish, I attended official classes when I first moved here in 2008 but grew frustrated with that class (and having other classes to teach and attend). Sadly most of my current (not very good) Finnish is due to what I can only describe as osmosis – eventually I just assimilated some words… and it’s a very slow process and, in many situations, I definitely rely too much on GoogleTranslate and the average Finn speaking English rather well. That was the case when I first lived in Finland and it’s still the case these days. Every once in a while I promise myself that I’ll start proper classes again but I always have excuses – too little time, too tired, none available when I’m free, I’d miss too many classes because of travels, etc. Excuses, excuses, excuses!
I must also note that during my years in Spain I was lucky enough to have been able to attend Spanish lessons organised by my previous employer – I got up to level B2 there (my work was all in English, the classes were there to make our everyday lives easier). Unsurprisingly, although my high school Spanish lessons allowed me to skip the introductory course, the stuff I learnt in school a decade prior was definitely not enough to get me by in actual Spain!
At one point I also attended a few Arabic lessons as we had a school offering Arabic, Persian and Hebrew lessons close by. While most classes were during my work hours, there was an introduction to Arabic at 6pm… and, boy oh boy, learning a new alphabet as an adult is something! On top of the new alphabet it was also really interesting to learn the actual words on which many Andalusian names are based (e.g. the Guadalquivir river/canal comes from al-wadi al-kabir) and also see the origin of some French words (e.g. a “toubib” means “doctor” in Arabic is also a slang term for doctor in French and, if I recall correctly, made its way into through the military).