I’m trying to localize my game where instead of using the Context + Source I’d just use Keys, however I have no clue how to go on about that as the wiki does NOT explain it 
Which APIs do I use and how? Examples would be great!
Why not use Context + Source?
I prefer using Keys than Context + Source because of how the game will be translated
If you have AutoLocalize on for a gui and it’s linked to a RootLocalizationTable, and the player is playing in whatever language you’ve provided translation for (via their RobloxLocaleId), it should recognize the translation in the table even without context given your formatting is correct.
Also if you want to test a language that ROBLOX doesn’t currently support, you can run this code in the command bar and Play Solo:
game:GetService("LocalizationService").ForcePlayModeRobloxLocaleId = "pt-br" --// brazilian portugese as an example
Sweet 
thanks so much saved me a lot of time!
One more question though, do I have to make a new csv for every language or?
No, I think you can put it all in one localization table. Just add a new column for each locale id.