How do I restore my maps navigation that was a built in app after being deleted

See the following from Delete built-in Apple apps on your iOS 12 or later device or Apple Watch - Apple Support

Restore a built-in app that you deleted

1. On your iOS device, go to the App Store.
2. Search for the app. Make sure that you use the exact name of the app. Find the correct name of built-in apps.
3. Tap  to restore the app.
4. Wait for the app to restore, then open it from your Home screen.

The Open indicates that it thinks it is already on your phone. If it doesn't run when you tap Open on that screen, I'm not sure what the reason is. The only thing I can think to suggest would be to restart your phone -- or wait for someone else here to reply or contact Apple Support (there is a link at the top right of this page).