Is it possible to reach a good command of English without studying hard?

[arlindomarco]

Do you think it's possible to reach a good command of English without
studying hard? I guess not!

[Torsten]

What do you mean by "studying hard"? Do you mean cramming grammar rules and vocabulary words into your head? If this is your definition of "studying hard", you won't reach a good command of English using this approach.
_________________
Test Of English for International Communication
TOEIC Preparation & TOEIC Vocabulary

[Jamie (K)]

However, you also won't reach a good command of English without studying. Those things Torsten mentions -- cramming grammar rules and vocabulary words -- will not have an immediate impact on your ability to speak and write in English, but they are important. Cramming the grammar rules trains what experts call your "monitor", which is your ability to keep a running check as to whether what you say is correct or not, and this helps you refine the accuracy of your language. Cramming vocabulary plants the words in your head, so that as you encounter more examples of their use, you will understand them and they will enter your active repertoire of words.

A person who does not study comes out with English that's just as bad as that of a person who only studies. Each person's English will be equally bad, but in a different way.