WhatsApp is backed up within the settings of the app. The same goes for Viber, One Note,and others. Google stuff I sync to Google drive. Microsoft to One drive. Things like photos, download, files in general I make copy to my computer.
I think that you'll need this google cloud backup and restore to fix the problem you're facing. Hope it's nothing serious and all your data is safe. Something similar has happened to me in the past and I lost all my data because I didn't have a proper backup and restore software in place.