Hi there!
You'll have to go to each subscription (if you have multiple) and then go to 'Resources' under Settings (You can find each subscription via portal.azure.com, login with your account and in the Search bar at the top type 'subscriptions'):
You should then be able to see all remaining Azure resources (alerts, etc) and delete these manually until each subscription is empty.
Hope this helps. If this solves your issues, please feel free to mark it as the accepted answer.