How can it be possible?

How can people learn more than 3-4 languages. Somebody tells that they can speak 8 (eight!) or 9 (nine!) or 10 (ten!) different languages. But are they fluently? I can't believe that.
Please enlighten me.
A

Some people have natural talent with languages.  I have friends who can speak 8 languages.  This is due to their background environment.  He was born in Vietnam but into a Chinese family.  So there are four languages learnt there!  Vietnamese, official school Chinese (Mandarin) and unofficial neighborhood lingo (Cantonese) and his native tongue (Teocheow), spent a few years in a Thai refugee camp where he also picked up Thai and Cambodian.  Then they went to France and so speaks French as well.  Now in the US, he speaks English.   However, they are all conversational standards.  His French and English can be considered a bit more academic but when it really comes down to mastering the academic standards, he still has a long way to go.  Of course, if he had chosen language as his career, I'm sure he will do even better. As in computer jargon, "breadth first depth last" instead of "depth first breadth last".

Some people have natural talent with  for languages. I have friends (?     a friend) who can(?)  speaks 8 languages.

This is due to their background environment(   ?       Your are not talking about architechture or stage sets, aren't you?). 

He was born in Vietnam but into a Chinese family  (?        clumzy, not so much English).

So there are four languages learnt there!(    Why do you say this way? Why not just  therefor he learnt fore languages. --- You were not writing in English actually, and you were telling stories! That's the why. )

Vietnamese, official school Chinese (Mandarin) and unofficial neighborhood lingo (Cantonese) and his native tongue (Teocheow), spent a few years in a Thai refugee camp where he also picked up Thai and Cambodian.                      (?               Is this English? )  Then they went to France and so speaks French as well. Now in the US, he speaks English.

However, they are all conversational standards. (         What do you mean by conversational standards? This is not English, and not Chinese either. Can you put it in English, for you are using English words, please? )

His French and English can be considered a bit more academic but when it really comes down to mastering the academic standards,  (           what do you mean? Which language are you speaking? I bet it is not English!)   he still has a long way to go.

Of course, if he had chosen language as his career, (       This is not English! Please speak English.)     I'm sure he will do even better. As in computer jargon, "breadth first depth last" instead of "depth first breadth last".      (        What the hell are you doing? Are you teaching English or trying your best to destroying English learning and teaching?   YOU MAY CHOOSE TO TEACH WHAT YOU CAN, AND YOU MAY CHOOSE NOT TO TEACH; BUT, FOR GOD'S SAKE, PLEASE DO NOT CHOOSE TO DESTROY. THANKS GOODNESS!)

How can it be possible?

How can people learn more than 3-4 languages. Somebody tells that they can speak 8 (eight!) or 9 (nine!) or 10 (ten!) different languages. But are they fluently? I can't believe that.
Please enlighten me.
====

I think most of us would be happy to speak 3 or 4 well! :)