Great topic! 
Well, I guess I learned many languages to some extent, but by far didn’t (yet?) get fluent in all of them. Still, knowledge of one language often helps with learning another, so it’s useful either way.
I’m from The Netherlands. My mothertongue is Dutch. My parents used to speak Dutch to my sister and me and Gronings (a West Low German dialect) to each other. So I learned Gronings only passively. And I also got exposed to Frisian in my childhood often enough to understand that for the most part.
In highschool I learned (apart from Dutch) English, French, German and Latin. Around that time I also taught myself some Spanish (which wasn’t taught at our school) as a hobby.
At university I studied Nordic languages (with Swedish as main language) and Fenno-Ugric languages (with Finnish as main subject). I took subsidiary courses at uni in Norwegian, Icelandic, Russian, Estonian and Czech. Old Norse was obligatory for Nordic languages. I can read Danish, but not actively speak it.
I understand Afrikaans, but that probably goes for all Dutch people.
Later in life I learned some more languages as a hobby and also brushed up some of the languages I learned in the past.
I learned a little Arabic and some Latvian and Bulgarian.
I also did almost all the languages offered at Duolingo, some only a little bit, some a lot.
Lately I’ve been mostly focussed on Korean, Japanese and Chinese.
Mongolian is still on the list. I also want to learn Albanian someday. And Biblical Aramaic … And Belarusian. Actually I’d like to learn all the Slavic languages, lol. And maybe some Celtic languages.
Here you can hear some Fenno-Ugric languages, including the less known ones:
https://www.youtube.com/watch?v=xxC0s9M16q0