by mistake I download all my documents in my Iphone how can I delete them from my Iphone?

Do you use iCloud for iCloud Drive? You probably do because that is how you have downloaded the documents. Are you accessing those from the Files app? If YES, then do not delete the documents without turning iCloud Drive OFF in iCloud. If you do not do this then whatever you delete on your iPhone will be also be deleted on your other devices using iCloud.

First, set iCloud Drive to OFF in iCloud and then begin deleting the documents on your iPhone. Open Settings ➡️ Apple ID (Your Name at Top) ➡️ iCloud ➡️ iCloud Drive: Set this to OFF.

Axel F.