Right next to where you clicked to get to the discussion page, there is another button that you can use to file a report that there is a problem. That will (eventually) get to the course creators who can do something about it. The discussion space is a forum for learners to ask questions and help each other learn. The course creators don't necessarily look here. For problems with the course itself, you need to file a report.
That button doesn't currently give an option for reporting a problem with the translation. :(
This is wierdly different on the computer and the phone app version. On the app version, there are no options, you just write what you like when you report. On computer, it's almost impossible to report errors if you use the word bank, since it automatically assumes that the English sentence is correct if you managed to guess it right. (The only way to report it is then to switch from word bank to keyboard, write what you think is the correct answer, and then report it is the page says you're wrong)
On the app version, there are no options, you just write what you like when you report.
That's only on the Android version. On iOS, there's just a "report" option that doesn't have anything more specific than just the fact that there was an error of some kind.