answer:In my experience, from seeing Spanish and German friends learning other languages, If you are younger than 10 it takes 5 years to lose, if you are 15 it takes 15 years to lose, and if you are 20 or over you have it for life. I’m 28, I learned 4 languages before I was 10, and natives tell me (as well as i know) that my accent is identical to a native one when I speak their language. I learned my 5th language when I was about 13, and natives tell me they some times can tell I’m not a native. The native speakers of any other languages I partially know, tell me it’s very obvious I’m not a native, but that my accent is better than average.