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I think translating is as "simple" as making sure to add text translations to the various text lists.
In the text categories you'll find a list of languages in a dropdown list - make sure yours is selected for the translation and then edit/add your translation to it. You may want to have a look at a career with translations to poke around in the file and see how they did it. Most of the time you just write in the correct boxes (usually the one to the left if there are two) and then click commit, and save the file. You'll figure out ingame if you did it right.
Making careers... never done it, and no idea if there are any video tutorials, but I don't doubt it.