wWhy are you studying English?

“Why do you study English?” is also correct

As tofor why I a’m studying English, first of all I must talkit’s mostly about population and information density.

You could also use “first and foremost” instead of “first of all”.
“First and foremost” = the most important
E.g. “The reason I study English is first and foremost its popularity…”

“First of all” = the first of many reasons
E.g. “First of all, I study English because it is popular. Second of all, I think it is fun. Third of all…”

Data shows that there are more than 1.5 billion people in the world speak English, including those who speak it as a second language.

It i’s estimated that there are more than 58 countries in the world that have English as their mother tongue, and it is said that if you can use English, you can access 20% of the languages in the world.

If I want to look up some new information, there i’s no doubt that I can’d get more informationresults by looking it up in English rather than in Japanese.

I a’m often asked if it I learn English for work or for traveling abroad, but the potential value of learning(speaking/understanding/knowing) English cannot be described in those terms.

wWhy are you studying English?

Couldan you please translatmake it more colloquially?

Yes, I can! Your formal English is pretty good. I will try to fulfill your request and make this more like casual, conversational English.

As tofor why I am study'm learning English, first of all I must tit's alkl about population and information density.

Data shows that there areThere's more than 1.5 billion people in the world, including those who speak it as a second language who speak English, assuming you count ESL speakers.

It i's estimated that there areere's more than 58 countries in the world that have English as their mother tonguethat speak English natively , and it i's said that if you can useknow English, you can accessget a leg up on 20% of the other languages in the world.

If I want to look up some new informationfind something out, there is no doubt that I can get more informationfind out more by looking it up in English than in Japanese.

I am often'm frequently asked if it i's for work or for traveling abroad, but the potential value of learnknowing English cannot be described in those termsis far greater than just that.

why are you studying English?

If I want to look up some new information, there is no doubt that I can get more information by looking it up in English rather than in Japanese.

I am often asked if it is am studying for work or for traveling abroad, but the potential value of learning English cannot be described in those terms.