Hello @StephanyJess
Thank you for contacting the Canvas Community. We're sorry to hear you've been experiencing issues with turning off all notifications. As an observer, you can go into your notification preferences and turn everything off. This should effectively stop any updates and notifications from Canvas:
https://community.canvaslms.com/t5/Observer-Guide/How-do-I-manage-my-Canvas-notification-settings-as...
Now you should be able to remove observed students from your Observer account! You can read about the details in the Canvas Deploy Notes (2021-03-17).
If you want to delete your account completely, you would want to reach out to the school directly.