How to use route overview_polyline points to open GPS navigation in app

I am currently developing a taxi driver app and would like to display navigation instructions to the driver based on a predefined route. I store the route in my database using the overview_polyline points value returned from the Google Maps Directions API. I also managed to display this route over a map in the website however I can't find anyway to display real time navigation instructions within the web app or at least open the user's device's default navigation app with the route saved in my database.

The web app is being developed in Angular.