Notification ads are easy to disable — just swipe left on the notification, and tap on Settings, then toggle Disable.
Your themes also include ads. To turn them off, open Themes, go to My Page > Settings and then disable Show ads, and Personalised recommendations.
Next is Downloads. Open the app, tap on the three dots menu > Settings, and turn off Show recommended content.
Now, the File Manager. You know the drill. Open the app > Settings > About, and turn off Recommendations.
In the Music app, go to Settings > Advanced Settings and then turn off Show ads, Show online recommendations on startup, and Personalised recommendations