The boy likes me, but I have always misunderstood him. What does he mean by sending such a short message? What should I do?

This eldest brother is very literary. Generally, only people who have experienced it can feel this way. I think he is discouraged. You don't know if boys will play again, because some things will never be the best, and you won't know how to cherish them. This is the present society and the present world. If you like him, please speak up. Even if you are rejected, let him know that you like him. That's it. Good luck.