I speak 3 languages fluently (English, French and Italian)

My mother tongue is Italian, however it's since been superseded by the other languages.

How do you accomplish this? Travel.

You absolutely need to immerse yourself to be fluent. Save your money. Make hard choices. Pick up and commit to spending 2+ years in a new country, society and culture.

It will be hard, but you will get a perspective that is lost on so many: what is the immigrant experience really like? what does it feel like to be victimized or discriminated against (assuming here that you're a white, English speaking American)? what does it feel like the first time you can successfully tell a joke? the first time you can give a presentation? the first time you can seduce a partner?

Get out there snowdragon, immerse yourself!