By default tooltip aggregates the data from one xAxis, but you can override it with a tooltip.formatter, see the link to the API: https://api.highcharts.com/highcharts/tooltip.formatter

The starting point can be like this:

tooltip: {
    shared: true,
    formatter: function () {
        let tooltipText = '<b>' + this.x + '</b>';
        this.points.forEach(point => {
            tooltipText += '<br/>' + point.series.name + ': ' + point.y;
        });
        return tooltipText;
    }
}

Please see a simplified config, where you can get the shared tooltip for multiple axes, I trust you will be able to adjust it for your project: https://jsfiddle.net/BlackLabel/pvr1zg26/