Great idea, just don’t use the right side button
As of Jan 6th, 2020, the main problem is that every two or three examples only plays sound with no option to check the answer or repeat the answer. All you can do is just click next and move on. But you don’t know you can’t check the answer until you’ve already listened to the answer.
Update: just use the left two buttons to navigate and replay. I’m not sure of the the purpose for the right side button.
Response from developer
Please make sure that you device is not switched to silent and that the volume is up. Then just tap the green button to have it start speaking. Please also note that you can install the higher quality Siri voices through iOS settings if you want better speech quality. Please get in contact if you need more assistance.