Getting user location in Xamarin with google play services

I want to show the current user location in an android app like the blue dot in GMaps. I searched online but I'm probably missing something important.

These are the classes or interfaces that my class derives from

public class TargetActivity : AppCompatActivity, IOnMapReadyCallback, Android.Locations.ILocationListener

This code is from my MainActivity, it's my first time programming on Android so I don't really know where to go from here.

    public GoogleMap _map;
    public MapFragment _mapFragment;
    LocationManager locationManager;
    string provider;

    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        SetContentView(Resource.Layout.Target);

        _mapFragment = FragmentManager.FindFragmentById(Resource.Id.map) as MapFragment;
        if (_mapFragment == null)
        {
            GoogleMapOptions mapOptions = new GoogleMapOptions()
                .InvokeMapType(GoogleMap.MapTypeTerrain)
                .InvokeZoomControlsEnabled(false)
                .InvokeCompassEnabled(true);

            FragmentTransaction fragTx = FragmentManager.BeginTransaction();
            _mapFragment = MapFragment.NewInstance(mapOptions);
            fragTx.Add(Resource.Id.map, _mapFragment, "map");
            fragTx.Commit();


        }
        _mapFragment.GetMapAsync(this);

        if (_map != null)
        {
            _map.UiSettings.ZoomControlsEnabled = false; 
            _map.UiSettings.CompassEnabled = true;  
            _map.MapType = GoogleMap.MapTypeTerrain;   

        }

        locationManager = (LocationManager)GetSystemService(Context.LocationService);
        provider = locationManager.GetBestProvider(new Criteria(), false);

        Location location = locationManager.GetLastKnownLocation(provider);
        if (location == null)
        {
            System.Diagnostics.Debug.WriteLine("no location");
        }
    }

    public void OnMapReady(GoogleMap googleMap)
    {
        MarkerOptions markerOptions = new MarkerOptions();
        markerOptions.SetPosition(new LatLng(16.03, 108));
        markerOptions.SetTitle("AAAA");
        googleMap.AddMarker(markerOptions);
    }

    public void OnLocationChanged(Location location)
    {

        double lat, lng;
        lat = location.Latitude;
        lng = location.Longitude;

        MarkerOptions markerOptions = new MarkerOptions();
        markerOptions.SetPosition(new LatLng(lat, lng));
        markerOptions.SetTitle("Posizione");
        _map.AddMarker(markerOptions);

        CameraPosition.Builder builder = CameraPosition.InvokeBuilder();
        builder.Target(new LatLng(lat, lng));
        CameraPosition cameraPosition = builder.Build();
        CameraUpdate cameraUpdate = CameraUpdateFactory.NewCameraPosition(cameraPosition);
        _map.MoveCamera(cameraUpdate);

    }

public void OnProviderDisabled(string provider)
        {
            //throw new NotImplementedException();

        }

        public void OnProviderEnabled(string provider)
        {
            //throw new NotImplementedException();
        }

        public void OnStatusChanged(string provider, [GeneratedEnum] Availability status, Bundle extras)
        {
            //throw new NotImplementedException();
        }