How to speak italian so fluently?

Learning it the right way and practicing it continuously with native speakers (preferably) or people who know Italian will help you achieve this goal, just like the way you do in English.

Dear Rana, I speak a fluent Italian as I am Italian mother tongue .
If you want to learn Italian you could enroll to Italian course and if if have a background on French language it will be more easy to understand the Italian grammar .
Sure, it is similar, but it can help you.
If you really like and want to learn it , you will learn and once you have attended some course, you should pass sometime in Italy , even just for vacation, in order to use the language.
In my opinion this is the best and quickest way to learn a language.
Wish you all the best and Good Luck !