how can I be sure that Icloud is totally empty ?

Hello wilfredo10,

It sounds like you are trying completely clear out everything from iCloud. We have a couple suggestions that should help.

The suggestions are going to depend on what device you are using.

If using and iPhone or iPad, tap on Settings > [your name] > iCloud > iCloud Storage. Here you should be able to see everything that is being stored in iCloud. You can access each App and delete the information. You can also prevent any apps from using iCloud again by tapping Settings > [your name] > iCloud and toggling all the apps listed here to off.

You will also want to sign out of iCloud: Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac - Apple Support

If you are looking to delete all the data associated with an Apple ID, including deleting the Apple ID itself, here is how: How to delete your Apple ID account - Apple Support

Additional information regarding information stored with Apple is available here: Understand and control the personal information that you store with Apple - Apple Support

We hope this helps.

Have a wonderful day!