Normally, once a message or chat is deleted by the sender on whatsapp, you won't see the contents anymore rather what you will see is "this message was deleted", unless you already quoted that message before it was deleted, you can't see or read it again but thanks to a third-party app called WhatsRemoved which helps you read deleted messages on whatsapp and it's free.

HOW TO READ DELETED WHATSAPP MESSAGES
1. Download Whatsremoved app from the Playstore by clicking here
2. You need to grant the app permissions on your Android smartphone after downloading. Don't worry, it will prompt you to do so.
3. Now, to view, read or see deleted Whatsapp messages that was sent to you, you will need to delete the deleted message notice from your WhatsApp messenger and close the WhatsApp messenger.
4. Finally, open the WHATSREMOVED app and navigate to Chats. There you will find the deleted message(s).
With this whatsapp trick, you don't need to be kept in the dark anymore whenever someone deletes his or her chats on whatsapp. Why not give it a try and see how it works.
You can also drop your testimonies below. Thank You.