var time = '';
var hour = 0;
var min = 0;
var sec = 0;
$.each($('.Lesson-List__length'), function(i, el) {
    min += parseInt($(el).text().split(':')[0]);
    sec += parseInt($(el).text().split(':')[1]);
    if(sec >= 60) {
        min += parseInt(sec/60);
        sec %= 60;
    }
    if(min >= 60) {
        hour += parseInt(min/60);
        min %= 60;
    }
});
time = 'It will take me ' + ((hour.toString().length == 1) ? '0' + hour : hour) + ':' + ((min.toString().length == 1) ? '0' + min : min) + ':' + ((sec.toString().length == 1) ? '0' + sec: sec) + ' hours to watch all those videos!';