Question

Нужна проверка грамматики, . nowadays there are about six thousand languages around the world. but many languages are endangered. and even greater numbers are extinct. at all times, the language was not only a means of communication, but also cultural heritage. language vanishes when its last speaker dies. together with them dwindles world culture and disappears a piece of history. for example, in the works of well-known british linguist david crystal, set an unknown language kasabe. his last native speaker died in 1996, leaving absolutely no information about the language and its history. however, what will happen to the world if languages will continue to disappear? rare languages will disappear first. as a result, many centuries later turn comes up languages "giants." this means that someday people will lose their ability to communicate with each other, world culture will be devastated, will begin a general degradation. humanity will return to the primitive age. do we want such an outcome?

Answer 1

 Nowadays there are about six thousand languages around the world. But many languages are endangered. And even greater number s are extinct. At all times,   language was not only a means of communication, but also part of cultural heritage. Languages vanish when their last speaker dies. With them dwindles the world’s culture and a piece of history disappears. For example, in the works of the well-known British linguist David Crystal, the formerly unknown to the world Kasabe language was recovered. Its last native speaker died in 1996, leaving absolutely no information about the language and its history. So, what will happen to the world if languages continue to disappear? Rare languages will disappear first. As a result, many centuries later the "giant" languages’ turn will comes. This means that some day people will lose their ability to communicate with each other, world culture will be devastated, a general degradation will start. Humanity will return to the primitive age. Do we want such an outcome?
Прежде, чем работать над грамматикой, надо бы поработать над стилистикой.
А то, коряво местами, не говоря уже о том, что - спорно. Но это уже вопрос к автору.