I have the same problem. I can't hear them on my phone - Android, but I can hear them on my computer. It's not just you. It's like you can't see the learning tips on the phone app and they are really useful so it's worth trying to use both systems.
The audio is wrong instead of saying hakuandika kitabu it's saying hukuandika kitabu...please fix this soon for others who have not passed the lesson, Thank you.