Foreign Accent

No, it is not true.

The notion that something magic changes between childhood and adulthood that prevents adults from achieving native fluency in a new language (particularly with respect to pronunciation) has long been treated as gospel by many linguists, but in fact it has never been proved, only presumed—and some independent-thinking linguists reject the notion as well.

Most people can learn to speak a language with any desired level of fluency at any age, given sufficient motivation and effort.

Well the question of accent is well known to methodology and phonetics.
I agree each individual has his or her own idiolect. But reaching nativelike
pronounciation when learning a second language is different. There are
tribes in south America whose people learn two or more other languages and they have native pronounciation. There were experiments e.g.
Americans could say single words in Chinese and a Chinese could not tell if the person wasn't a native. Yet there are some people who manage to get a nativelike accent.
If you are interested read some books on methodology and teching English.