I use iOS 7.1 with Japanese on iPhone 4S. Duolingo had worked properly on the environment. I am learning Spanish course for English speakers.

I updated Duolingo to version 4.0 yesterday and then the language of Duolingo was forced to switch to Japanese. The language setting does not work and I cannot change the language to English. In addition, while studying the Spanish course, I encountered speaking questions in English, not in Spanish.

I understand that switching the language of iOS to English solves the situation, but I do not want to do so.

Best,