Virino is going to trick me so much because I am used to words ending in O being masculine.
All nouns in Esperanto end in -o, so you only need to worry about what comes before (in this case, the -in- affix).
Technically the suffix is just -in, just -o being the noun marker, but that's how it goes. Make sure you read the Tips & Notes before starting each skill - most questions are explained there beforehand.
Wow! I don't have an answer, but I'd like to congratulate you on all those languages you're learning