Hello @Nour Hasan 

To achieve that you can explore the Google Maps API by doing the following:

1. Use a site to create the JSON with your styles (like this one or Google's one here) and copy the JSON
   
   
2. In the Map Initialized event add a JavaScript node with the following script:

   • const stylesJSON = [
         {
             "featureType": "all",
             "elementType": "all",
             "stylers": [
                 {
                     "visibility": "on"
                 }
             ]
         },
         {
             "featureType": "all",
             "elementType": "labels",
             "stylers": [
                 {
                     "visibility": "off"
                 },
                 {
                     "saturation": "-100"
                 }
             ]
         },
         {
             "featureType": "all",
             "elementType": "labels.text.fill",
             "stylers": [
                 {
                     "saturation": 36
                 },
                 {
                     "color": "#000000"
                 },
                 {
                     "lightness": 40
                 },
                 {
                     "visibility": "off"
                 }
             ]
         },
         {
             "featureType": "all",
             "elementType": "labels.text.stroke",
             "stylers": [
                 {
                     "visibility": "off"
                 },
                 {
                     "color": "#000000"
                 },
                 {
                     "lightness": 16
                 }
             ]
         },
         {
             "featureType": "all",
             "elementType": "labels.icon",
             "stylers": [
                 {
                     "visibility": "off"
                 }
             ]
         },
         {
             "featureType": "administrative",
             "elementType": "geometry.fill",
             "stylers": [
                 {
                     "color": "#000000"
                 },
                 {
                     "lightness": 20
                 }
             ]
         },
         {
             "featureType": "administrative",
             "elementType": "geometry.stroke",
             "stylers": [
                 {
                     "color": "#000000"
                 },
                 {
                     "lightness": 17
                 },
                 {
                     "weight": 1.2
                 }
             ]
         },
         {
             "featureType": "landscape",
             "elementType": "geometry",
             "stylers": [
                 {
                     "color": "#000000"
                 },
                 {
                     "lightness": 20
                 }
             ]
         },
         {
             "featureType": "landscape",
             "elementType": "geometry.fill",
             "stylers": [
                 {
                     "color": "#4d6059"
                 }
             ]
         },
         {
             "featureType": "landscape",
             "elementType": "geometry.stroke",
             "stylers": [
                 {
                     "color": "#4d6059"
                 }
             ]
         },
         {
             "featureType": "landscape.natural",
             "elementType": "geometry.fill",
             "stylers": [
                 {
                     "color": "#4d6059"
                 }
             ]
         },
         {
             "featureType": "poi",
             "elementType": "geometry",
             "stylers": [
                 {
                     "lightness": 21
                 }
             ]
         },
         {
             "featureType": "poi",
             "elementType": "geometry.fill",
             "stylers": [
                 {
                     "color": "#4d6059"
                 }
             ]
         },
         {
             "featureType": "poi",
             "elementType": "geometry.stroke",
             "stylers": [
                 {
                     "color": "#4d6059"
                 }
             ]
         },
         {
             "featureType": "road",
             "elementType": "geometry",
             "stylers": [
                 {
                     "visibility": "on"
                 },
                 {
                     "color": "#7f8d89"
                 }
             ]
         },
         {
             "featureType": "road",
             "elementType": "geometry.fill",
             "stylers": [
                 {
                     "color": "#7f8d89"
                 }
             ]
         },
         {
             "featureType": "road.highway",
             "elementType": "geometry.fill",
             "stylers": [
                 {
                     "color": "#7f8d89"
                 },
                 {
                     "lightness": 17
                 }
             ]
         },
         {
             "featureType": "road.highway",
             "elementType": "geometry.stroke",
             "stylers": [
                 {
                     "color": "#7f8d89"
                 },
                 {
                     "lightness": 29
                 },
                 {
                     "weight": 0.2
                 }
             ]
         },
         {
             "featureType": "road.arterial",
             "elementType": "geometry",
             "stylers": [
                 {
                     "color": "#000000"
                 },
                 {
                     "lightness": 18
                 }
             ]
         },
         {
             "featureType": "road.arterial",
             "elementType": "geometry.fill",
             "stylers": [
                 {
                     "color": "#7f8d89"
                 }
             ]
         },
         {
             "featureType": "road.arterial",
             "elementType": "geometry.stroke",
             "stylers": [
                 {
                     "color": "#7f8d89"
                 }
             ]
         },
         {
             "featureType": "road.local",
             "elementType": "geometry",
             "stylers": [
                 {
                     "color": "#000000"
                 },
                 {
                     "lightness": 16
                 }
             ]
         },
         {
             "featureType": "road.local",
             "elementType": "geometry.fill",
             "stylers": [
                 {
                     "color": "#7f8d89"
                 }
             ]
         },
         {
             "featureType": "road.local",
             "elementType": "geometry.stroke",
             "stylers": [
                 {
                     "color": "#7f8d89"
                 }
             ]
         },
         {
             "featureType": "transit",
             "elementType": "geometry",
             "stylers": [
                 {
                     "color": "#000000"
                 },
                 {
                     "lightness": 19
                 }
             ]
         },
         {
             "featureType": "water",
             "elementType": "all",
             "stylers": [
                 {
                     "color": "#2b3638"
                 },
                 {
                     "visibility": "on"
                 }
             ]
         },
         {
             "featureType": "water",
             "elementType": "geometry",
             "stylers": [
                 {
                     "color": "#2b3638"
                 },
                 {
                     "lightness": 17
                 }
             ]
         },
         {
             "featureType": "water",
             "elementType": "geometry.fill",
             "stylers": [
                 {
                     "color": "#24282b"
                 }
             ]
         },
         {
             "featureType": "water",
             "elementType": "geometry.stroke",
             "stylers": [
                 {
                     "color": "#24282b"
                 }
             ]
         },
         {
             "featureType": "water",
             "elementType": "labels",
             "stylers": [
                 {
                     "visibility": "off"
                 }
             ]
         },
         {
             "featureType": "water",
             "elementType": "labels.text",
             "stylers": [
                 {
                     "visibility": "off"
                 }
             ]
         },
         {
             "featureType": "water",
             "elementType": "labels.text.fill",
             "stylers": [
                 {
                     "visibility": "off"
                 }
             ]
         },
         {
             "featureType": "water",
             "elementType": "labels.text.stroke",
             "stylers": [
                 {
                     "visibility": "off"
                 }
             ]
         },
         {
             "featureType": "water",
             "elementType": "labels.icon",
             "stylers": [
                 {
                     "visibility": "off"
                 }
             ]
         }
     ];
     
     OutSystems.Maps.MapAPI.MapManager.GetMapById($parameters.MapId)._provider.setOptions({styles:stylesJSON});
     //$parameters.MapId is the identifier of the Map block
     				

3. Check that the style is properly applied:

I hope it helps.

Cheers,
GM