Highcharts - Link Two BAR Charts in ONE

HTML

<script src="http://code.highcharts.com/highcharts.js"></script>
<div id="GraphContainer"></div>

JavaScript

$(document).ready(function(e) {
        
	    var perShapeGradient = {
            x1: 0,
            y1: 0,
            x2: 0,
            y2: 1
        };
    
		chart = new Highcharts.Chart({
			chart: {
				renderTo: 'GraphContainer',
				height:	275,
				marginLeft: 120,
				marginTop: 30
			},
            colors: 
			[
				{
					linearGradient: perShapeGradient,
					stops: 
					[
						[0, 'rgba(186, 186, 186, 1)'],
            			[1, 'rgba(232, 232, 232, 0.8)']
					]
				}
      		],
			title: {
				text: null
            },
			plotOptions: {
				line: {
					lineWidth: 1,
					marker: {
						radius: 6,
						fillColor: '#fff',
						lineColor: '#e10019',
						lineWidth: 1.5,
						states:
						{
							hover:
							{
								radius: 8,
								fillColor: '#e10019',
								lineColor: '#fff',
								lineWidth: 2
							}
						}
					}
				}
			},
			xAxis: {
				categories: ['13 May', '20 May'],
				title: 'Week Commencing'
			},
			yAxis: [{
				labels: {
					endOnTick: true,
					formatter: function() {
						return this.value + '%';
					},
					style: {
						color: '#e10019',
						fontSize: 10
					}
				},
				title: {
					text: '% rated as 4 or 5',
					rotation: 270,
					offset: 75,
					style: {
						color: '#f49fa8',
						fontSize: 11,
						fontWeight: 'normal'
					}
				},
				max: 100,
				opposite: true
			}, {
				gridLineWidth: 0,
				title: {
					text: 'Number of responses',
					style: {
						color: '#888',
						fontSize: 11,
						fontWeight: 'normal'
					}
				},
				labels: {
					formatter: function() 
					{
						x = this.value.toString();
						var pattern = /(-?\d+)(\d{3})/;
						while (pattern.test(x))
							x = x.replace(pattern, "$1,$2");
						return x;
					},
					style: {
						color: '#888',
						fontSize: 10
					}
				}
	
			}],
			tooltip: {
				formatter: function() {
					
					var unit = {
					'Applicable': '',
					'Sentiment': '%'
					}[this.series.name];

					return 'Week Commencing ' +...