You can ping the site's maintainer, @Dennis, in talk.tryitonline.net. Bug reports and language requests tend to be resolved withing the same day of them being submitted, because Dennis is awesome.
There's also https://gitter.im/tryitonline/Requests (requires a Gitter account), https://github.com/TryItOnline/tryitonline/issues (requires a GitHUb account), and email (feedback@tryitonline.net).