I’m not so sure. Again speaking only from my observations. Some people i know have migrated to another country in their early twenties, taken on their new host

I’m not so sure. Again speaking only from my observations. Some people i know have migrated to another country in their early twenties, taken on their new host language as their core. E.g partner and kids with this new language. Yet still after 40 years they are not as comfortable as with their original language.