There is a file generated in src/legacy/dev-application/languages/creator/fi.php.missing, which contains missing strings for the Finish language.

The missing translations should be added, inside the same .missing file.

To be assigned this issue, you'll have to be a native speaker of the language. You can prove it to me by adding me on LinkedIn so I can see your profile and we can chat a little about contributing. I want to have real people, and really good translations here, not some generated stuff.