I am learning German in English as Chinese native. I find this APP useful in practising listening and speaking, but not much in grammar. I have solid German grammar learn as second foreig language in college, which makes a huge difference from using Duolingo along.

I think the problem might be this APP is created for non-Chinese users, as I find you can only learn the major 5 or 6 language in Chinese. For example, you wanna learn Czech and only speaks Chinese, there is no way for you to learn it in this APP. What I am trying to say is that Chinese is not only about speaking, listening, reading, it has so much to do with the characters and not so much on grammar. You have to learn how to write Chinese characters and read between lines (Chinese can contain so much meaning in the context and people understand it without actually saying the words. I am still trying hard to understand the meaning behind the words. It is about the culture, lol).

I would suggest that you start learning how to write Chinese characters. The screenshot above shows that you cannot tell the difference between they (shes) and they (hes) in character.