Lighten WhatsApp for Android
WhatsApp clenaer is the solution to your problem.
On the home screen it summarizes the space that each file type (Picture, Audio, Video, Documents) occupies, dividing them into those received from the responses to them.
You can select individual or group files and delete them, move them to another folder or SD, or transfer them to Dropbox.
If you're not sure, you can see a preview of the file in order to make sure that you delete or move the right one.
If you already have a copy, you can also select all files sent by category and delete them permanently.
Also you can select all of the same SIZES file to find duplicate files.
You will not lose anything, but you will have the smartphone of new light and fluid.