Can you tell me ?!(How to compose a good song?)?

That has been argued about for years, ages even. Generally, a life event works well. Or an opinion, to a lesser degree. It is a matter of stating your feelings. Like a very compressed story, really. John Prine wrote some good stuff, even though it was mostly sang by others. Like Jimmy Buffet, for example. The point I make, is a lot of his songs were a snapshot of a moment or a brief period of his life. So use your life as a guide, maybe a sad moment, or even a happy one, to get material from. Write it all down, condense it to just the essentials of what you wish to make others feel, and you have a song.