I really want it.

I want to go to live to in United States, because there I will get to know a lot places and my English will /improve/become better/.

I really want it.

I want to go to live to United States, because there I will know a lot places and my english will be better.

I want to go to live in the United States because then I will know a lot of places and my English will be better.

There are many ways to say and write something.  You could write your article in my different ways and still mean the same thing. What you wrote is fine. I understand what you wanted to say.