How to update translation

Hello and thank you for your hard work.

I am new here and installed Frontaccounting at the shared hoster Netcup with no problems.

But installing language package went into the message "Cannot download repo index file." This was my first problem.

Second I downloaded mo and po files local and installed it manually. But I found many strings untranslated (german). So I'd like to help in german translation. Is there any central platform where we can do it? If not, where can I get a file with all translatable strings to complete german translation? And where to send it to help other people?

Thank you