I have a(n English) friend who moved to Finland as an adult (in her 30s) and is now fluent in Finnish (and English, just the two languages for her) so it is cer

I have a(n English) friend who moved to Finland as an adult (in her 30s) and is now fluent in Finnish (and English, just the two languages for her) so it is certainly possible. I have very jealous of your friend’s multi-lingual son though!