Can I learn English alone/by myself/on my own?
Yes, resounding Yes, but this is not a good question, this is not the question you should be asking
The 1 billion dollar question is:
Is there any other way?
NO, there is no other way.
The ONLY way to learn a foreign language is alone/by myself/on my own. Every one who has even mastered a foreign language as an adult, has done it alone, outside the classroom
There is simply no other way!