Zend certified PHP/Magento developer

Magento website backups

Sorry for the low level of this question; I’m a beginner, and I’m kinda unaware of the extent of my own ignorance at this point.

I need to back up my Magento 2.2.2 website before upgrading to v2.4.

So I transferred all the files (minus ~12k files, which gave an error in FileZilla) to local storage using FTP. The resulting directory is over 800 GB in size.

Is this a normal size for a Magento website? Is there a faster/more convenient way to create a full backup?

(Already tried System -> Tools -> Backups in the admin panel, and I can only make Database backups. System or Database & Media backups produce a “We can’t create this backup right now” error).