Duolingo is the best app for learn if you really want to learn.
In this app you can learn many foreign languages including english.
For english you have to good hindi.
For other foreign languages you have to good english.
Its a perfacwt way to learn english.
It has one more feature that you want it learn from basic means from start or you know something else.
This is the best app.
If you want to learn.
I am sure you will like it.