Need Professional Audio done - I’ve re-exported and it fixed the issue

Hello there, I'd like to master a piano recording of my son. Track currently has a buzzing sound. Want to make it sound professional.Am after a quote for the same

Additional info:
The tracks are cleaned, tuned, and and the song is ready to be mixed. I'll need you to master it too if possible. I don't have a hard deadline for this. Check out the song I attached. The song has less than 10 tracks recorded that need mixing. I'm interested in working with a very experienced mixer.