Q: iCloud / whatsupp Problem

Goodmorning everyone.

I have a problem with iCloud (not icloud drive)

I have a few days changed my old iphone 5 with a new iPhone 6s.

I have deliberately not restored from an old backup iCloud or iTunes, because I wanted a new configuration.

I still used my only apple id to reconfigure the new iCloud iPhone 6s.

I also reinstalled Whatsupp, but the backup section of the chat is displayed: last backup, never.

Instead I backed up I did.

It also does not allow me even to make a backup of the new installation of whatsupp.

In the iCloud setup I read that the space of 5GB is low.

If I access from www.icloud.com does not see any content, I see that in every case all the space is occupied by the old iphone 5.

But I do not see any photos (which are usually the ones who more than anyone else take up space).

What can I do to restore the whatsupp chat and then to delete old backups iCloud?

Thank you very much for your attention.

Fabio.