WhatsApp is a famous messaging app used by billions of smartphone users globally. Back in July 2017, WhatsApp announced 1.3 billion active users from 180 countries. Apart from the text messages, WhatsApp users also share media (including photos, videos, GIFs, contacts, locations, audio messages and documents).
Steps:
Delete media from a chat or group using “Storage Usage”
Open WhatsApp on your Android phone.
Go to WhatsApp Settings by tapping on the 3 vertical dots and choosing “Settings“.
Now tap on “Data and storage usage” and choose “Storage usage“. WhatsApp will take some time to analyze the database and calculate how much storage space is being used by each group/chat.

4. Tap on the group/contact for which you want to delete all the media files. You can use the search functionality if you have a lot of contacts or groups. WhatsApp will now show you how many media files exist on your phone and how much space is being used by each media type. So, you can see Photos, GIFs, Videos, Audio and Documents.
5. Tap on “Manage Messages” at the bottom and select (using the checkbox) the media which you want to delete. By default, all items are checked. Those with the checkbox checked means that they are selected for deletion. NOTE: Uncheck Text Messages else you will lose the text chats as well.