There are a few ways to save data in WhatsApp while still receiving notifications and messages. First, disable the app’s ability to download media on mobile data. From this section, you can check or uncheck the downloading of photos, audio, videos and documents via mobile data. This way, you need to tap on the file to actually download it. Videos, in particular, are huge data hogs, so we’d recommend leaving this unchecked.
This is done via Settings > Data and storage usage > When using mobile data. Remove all marks
You can now download files manually. Thats All!