Hey Indonesian development team. Having worked through a chunk of the course today I've noticed quite a few English errors that would be relatively simple to fix. Would you like a native English speaker to assist? I am not fluent in Indonesian but I have a fairly good knowledge of the language.
Same observation and offer of assistance here; my (non-Duolingo learned) Indonesian is imperfect but I have experience in linguistics, education and writing/editing. Would be willing to help with the English side of things if help is desired.
I concur with Robert - there are a lot of basic English errors throughout the course.
I offer my services as well. A big first start would be to allow for the option to mark the English sentence as unnatural. I just got through 4 malformed English sentences and didn't have the option to mark them as unnatural or inaccurate. I'm willing to help.