The English is poorly translated, and the app is buggy. Sometimes explanations for certain answers are given, sometimes not, which is frustrating. Also, the reason why this app has the 5 star reviews is that the app gives you the ability to save questions for future reference. Even with the paid version of the app, they limit you to only 5 marked questions. To extend this, they require you give them a give Star rating, even though I've already paid for the app.