Why I can't see my files and pictures in my icloud account

Did you set up iCloud Photos on your device, so that all pictures will be copied to iCloud and all other devices?

Set up and use iCloud Photos - Apple Support

But, deleting photos on one connected device will also delete those pictures or data in iCloud.

The only way to delete photos and other data without removing them from iCloud would be archiving them before:

Archive or make copies of the information you store in iCloud - Apple Support