If I delete my WhatsApp data, will my data disappears from my iCloud backup, too? I want to delete the WhatsApp data from my iPhone in order to make some free space. But If I will do it, at the next backup, will my old backup disappear too?
Neither the iOS iCloud backup nor the WhatsApp iCloud backup are versioned, so yes: once you delete WhatsApp chats the next backup run will have them disappear from the backup as well.