Can I keep my WhatsApp videos on the cloud?
WhatsApp doesn't have the feature to save videos to a cloud. As soon as you download a video sent to you, WhatsApp deletes it. 

You can have all your WhatsApp messages and media backup to Google drive, but that's not easily accessible unless you restore all messages from Google drive (usually done when switching phones or data loss.) 

My suggestion is to get an app that will backup your phots/videos. Like Google phots. 

Or you can move all videos to your SD card and then delete them from WhatsApp.