There might be slight, isolated cases where users lost their saved progress, forcing them to repeat the lesson. We are working hard to make sure the app is always stable and this is avoided. We are working towards continuous app improvements.
In order to let us know exactly what happened, please go to your profile in the app and click on “Report technical issue”. This enables us to see exactly what happened technology-wise. Try to provide as much information as possible so our support team can better understand your issue. We will get back to you within 24-48 hours to help resolve it!