Hi Michel, others may have more detailed information, but I can tell you that the course is saved on your computer, not anywhere online.
If you intend on access files outside of the authoring tool for a course you created using the authoring tool, the only option there is to "Export source code" and then edit the files as if you were using Adapt framework without the authoring tool. This allows more flexibility (but knowledge).
You basically choose to either A) create/edit courses using the authoring tool, or B) create/edit courses without the authoring tool, which is more hands on and code oriented.
For localisation, I don't think that the authoring tool has any feature to help with that (yet). But using the adapt framework without the authoring tool does have an import/export feature to get at text and your team can manually translated content. Look here for more info on that: https://github.com/adaptlearning/adapt_framework/wiki/Course-Localisation