There are many options on that question. lmbo but umm ;; what do আপনি feel i your heart. its easier that way than any other way at all.. here are some that i would write 1.)Love 2.)Nature and maybe something rock like that has a playful feel to it :] idk if this helps but anything is worth a shot
আপনি could write romance অথবা even a life story. I write songs too and it's usual about something people my age can relate to. But that is my style. I would recommend something that আপনি like and আপনি would enjoy. Like if আপনি like pop then write pop. অথবা if theres something happening in your life that is not to personal then আপনি could turn it into a song. Hope this helps!