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