Correção de texto: Carnival

Hiii. I've sent this message in an app:

One of the major events in Brazil is Carnival. Carnival is famous for its joy and different kinds of dance. It happens every year and generally in February. Every year Carnival brings together people from all cultures that's why it can be considered as the biggest festive event in Brazil.

And I've received this correction:

One of the major events in Brazil is the Carnival. The Carnival is famous for its joy and different kinds of dance. It happens every year and generally in February. Every year the Carnival brings the people from all cultures together that's why it can be considered as the biggest festivity in Brazil.

I have three questions: is it right use "the" before "Carnival", once Carnival is a personal name in this case? Do I really need to separate the phrasal verb "bring together" in this case? If the answer is yes, why do I need to do it? Further, the way how I used "festive" is wrong?