Turn off notifications: Android
Account settings: https://youtu.be/KON6JC6j2Q0?t=29s
App settings: https://youtu.be/KON6JC6j2Q0?t=50s
Channel settings: https://youtu.be/KON6JC6j2Q0?t=1m39s
Device settings: https://youtu.be/KON6JC6j2Q0?t=1m58s
To learn more, please visit the YouTube Help Center: https://www.youtube.com/help