To ensure that you can receive notifications from Kitab Sawti, please check your notification settings for the app in your phone settings. If it is already enabled, then please check the setting inside the Kitab Sawti app, you can find it in the Settings tab.
To make sure you receive notifications, you can toggle the switch to off and then back to on again to ensure your setting is saved.
Some device models have very aggressive battery saving features that disable notifications for apps. To avoid this, you should disable all battery saving features for the Kitab Sawti app.