This app supports Android's backup and restore feature, so please back up your Android device itself. For details, see "Back up or restore data on your Android device" on Google's website.
Switching from an iPhone
Open this app on the iPhone and tap "Data Backup/Restore" in the app's settings screen to export your data,
then upload the exported data to Google Drive or a similar service
so that it can be accessed from the Android device.
Next, open this app on the Android device, tap "Data backup/restore" in the app's settings screen,
tap "Restore backup data" → "Select the file directly",
and select the backup data to restore it.
This transfers your data correctly.