infowindow question

want to add an infowindow in overley's marker

HTML

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>Map-Test</title>
    <script src="https://cdn.jsdelivr.net/gmap3/7.2.0/gmap3.min.js"></script>
    <script type="text/javascript" src="https://maps.googleapis.com/maps/api/js?key=AIzaSyBzlZxe7Hg60lCe2pXEDiVY7we11YphLZI&region=GB"></script>
    <script src="https://canvasjs.com/assets/script/canvasjs.min.js"></script>
    <script src="https://www.amcharts.com/lib/3/amcharts.js"></script>
    <script src="https://www.amcharts.com/lib/3/gauge.js"></script>
    <script src="https://www.amcharts.com/lib/3/plugins/export/export.min.js"></script>
    <link rel="stylesheet" href="https://www.amcharts.com/lib/3/plugins/export/export.css" type="text/css" media="all" />
    <script src="https://www.amcharts.com/lib/3/themes/light.js"></script>
</head>
<body>
    <div id="map"></div>

    <div id="ShanhuaChart1"></div>
    <div id="ShanhuaChart2"></div>

</body>
<script src="app.js"></script>

</html>

CSS

#map {
        height: 100%;
        width: 100%;
    }

    html,
    body {
        height: 100%;
        margin: 0;
        padding: 0;
    }

    #ShanhuaChart1 {
        width: 40%;
        height: 20%;
    }

    #ShanhuaChart2 {
        width: 200px;
        height: 200px;
    }

JavaScript

// test gmap3 feature
// set lat/lng for map's center
var uluru = {
    lat: -25.363,
    lng: 131.044
};
let markerShanhua = [23.11509722, 120.2971417];

// set map
let map = $('#map').gmap3({
    zoom: 10,
    address: "Taiwan Tainan",
    mapTypeId: google.maps.MapTypeId.ROADMAP
});


// draw charts
map.marker({
    position: markerShanhua
}).overlay({
    position: markerShanhua,
    content: ShanhuaChart1,
    x: 30,
    y: -50
});

map.marker({
    position: markerShanhua
}).overlay({
    position: markerShanhua,
    content: ShanhuaChart2,
    x: -200,
    y: -75
});

// set markers with infowindow
map.marker({
    address: "Taiwan Tainan"
}).infowindow({
    content: "Hello from Uluru"
}).then(function (infowindow) {
    console.log("this is this");
    console.log(this);
    console.log("this is infowindow");
    console.log(infowindow);
    var map = this.get(0);
    var marker = this.get(1);
    console.log("this is map");
    console.log(map);
    console.log("this is marker");
    console.log(marker);
    marker.addListener('click', function () {
        infowindow.open(map, marker);
    });
});

// do draw charts by html element
//Shanhua
var _ShanhuaChart1 = new CanvasJS.Chart("ShanhuaChart1", {
    title: {
        text: "AQI"
    },
    animationEnabled: true,

    backgroundColor: "rgba(255,255,255,0.5)",

    data: [{
        type: "spline",
        dataPoints: [{
                x: new Date('2018-05-12 03:00:00'),
                y: 460
            },
            {
                x: new Date('2018-05-12 04:00:00'),
                y: 450
            },
            {
                x: new Date('2018-05-12 05:00:00'),
                y: 500
            },
        ]
    }]
});
_ShanhuaChart1.render();
var _ShanhuaChart2 = AmCharts.makeChart("ShanhuaChart2", {
    "hideCredits": true,
    "type": "gauge",
    "theme": "light",
    "axes": [{
        "axisAlpha": 0,
        "tickAlpha": 0,
        "labelsEnabled": false,
        "startValue": 0,
...