be careful with frequencies, even if it is a demo, it is not good then voice and piano go in contrast with frequencies; anyway the sample you use good even if the hook is too ripetitive; you have to try to be more various with the melodic line, and the beats; when a melody or something in the song keeps the mind of the listener , it is the most important thing, because he then say “i buy”; the idea is good , i feel it, but you have to work on it again, best luck and keep it up.