[Fedora-trans-de] How to upload .po file to translate.zanata?

Hi, Sorry for bothering this list again with my rookie questions. I translated (part of) blivet-gui into German (de) and noticed that the f24-branch also requests translations for de-DE. How can I upload the .po file of de-translations to de-DE? Or is this maybe not even needed? Will a system automatically default to de if de-DE is not available? The other thing, sometimes I see a master branch, I assume that all "release branches" (such as f24, devel, rhel7...) are forked from this master. What's the strategy if there is no master? Will the next release be forked from the latest version? What if the release branches all have different progress of translation (say 41%, 48%, and 66%). What this question basically means, that it isn't obvious to me to what branch to contribute (even in the case that there is a master. So, what would be of higher priority? A master or f-24? Will the changes to f-24 be merged back to master?). Beste Grüße, Florian