Bootstrap Css Mobile first resizing issue - html

Question

having trouble with resizing when running on mobile. Elements in id="mustTake" are overlaying each other when in mobile. I am trying to achieve the same look as two elements on top when in mobile.
header {
background-color: #8FBCDB;
}
.container {
padding-top: 10px;
}
body {
background-color: #E0EEEE;
}
#profile {
position: absolute;
right: 7%;
top: 0%;
z-index: 1;
}
.panel .panel-info {
position: absolute;
z-index: 1;
}
.container h1 {
z-index: 1;
}
.myButton {
background-color: #44c767;
-moz-border-radius: 14px;
-webkit-border-radius: 14px;
border-radius: 14px;
border: 1px solid #18ab29;
display: inline-block;
cursor: pointer;
color: #ffffff;
font-family: Georgia;
font-size: 14px;
font-weight: bold;
padding: 4px 10px;
text-decoration: none;
text-shadow: 0px 1px 0px #2f6627;
}
.myButton:hover {
background-color: #5cbf2a;
}
.myButton:active {
position: relative;
top: 1px;
}
.myButton1 {
background-color: #FFA500;
-moz-border-radius: 18px;
-webkit-border-radius: 18px;
border-radius: 18px;
border: 1px solid #18ab29;
display: inline-block;
cursor: pointer;
color: #ffffff;
font-family: Georgia;
font-size: 19px;
font-weight: bold;
padding: 4px 10px;
text-decoration: none;
text-shadow: 0px 1px 0px #2f6627;
}
.myButton1:hover {
background-color: #EE9A00;
}
.myButton1:active {
position: relative;
top: 1px;
}
.table-striped tr {
font-size: 18px;
}
.table-striped th {
font-size: 20px;
}
.timeline {
list-style: none;
padding: 0;
position: relative
}
.timeline:before {
top: 0;
bottom: 0;
position: absolute;
content: "";
width: 2px;
background-color: #fff;
left: 40px;
margin-left: -1.5px
}
.timeline>li {
margin-bottom: 50px;
position: relative;
min-height: 50px
}
.timeline>li:before,
.timeline>li:after {
content: " ";
display: table
}
.timeline>li:after {
clear: both
}
.timeline>li .timeline-panel {
width: 100%;
float: right;
padding: 0 20px 0 100px;
position: relative;
text-align: left
}
.timeline>li .timeline-panel:before {
border-left-width: 0;
border-right-width: 15px;
left: -15px;
right: auto
}
.timeline>li .timeline-panel:after {
border-left-width: 0;
border-right-width: 14px;
left: -14px;
right: auto
}
.timeline>li .timeline-image {
left: 0;
margin-left: 0;
width: 100px;
height: 80px;
position: absolute;
z-index: 100;
background-color: ;
color: #fff;
border-radius: 5%;
border: 7px solid #FFCC33;
text-align: center;
}
timeline>li .timeline-image1 {
left: 0;
margin-left: 0;
width: 100px;
height: 80px;
position: absolute;
z-index: 100;
background-color: ;
color: #fff;
border-radius: 5%;
border: 7px solid #f1f1f1;
text-align: center;
}
.timeline>li .timeline-image h4 {
font-size: 10px;
margin-top: 12px;
line-height: 14px;
}
.timeline>li.timeline-inverted>.timeline-panel {
float: right;
text-align: left;
padding: 0 20px 0 100px;
}
.timeline>li.timeline-inverted>.timeline-panel:before {
border-left-width: 0;
border-right-width: 15px;
left: -15px;
right: auto
}
.timeline>li.timeline-inverted>.timeline-panel:after {
border-left-width: 0;
border-right-width: 14px;
left: -14px;
right: auto
}
.timeline>li:last-child {
margin-bottom: 0
}
.timeline .timeline-heading h4 {
margin-top: 0;
color: inherit
}
.timeline .timeline-heading h4.subheading {
text-transform: none
}
.timeline .timeline-body>p,
.timeline .timeline-body>ul {
margin-bottom: 0
}
.timeline:before {
left: 50%
}
.timeline>li {
margin-bottom: 100px;
min-height: 100px
}
.timeline>li .timeline-panel {
width: 41%;
float: left;
padding: 0 20px 20px 30px;
text-align: right
}
.timeline>li .timeline-image {
width: 100px;
height: 100px;
left: 50%;
margin-left: -50px
}
.timeline>li .timeline-image h4 {
font-size: 13px;
margin-top: 16px;
line-height: 18px
}
.timeline>li.timeline-inverted>.timeline-panel {
float: right;
text-align: left;
padding: 0 30px 20px 20px
}
.timeline>li {
min-height: 170px
}
.timeline>li .timeline-panel {
padding: 0 20px 20px 100px
}
.timeline>li .timeline-image {
width: 270px;
height: 170px;
margin-left: -133px;
}
.timeline>li .timeline-image h4 {
margin-top: 40px
}
.timeline>li.timeline-inverted>.timeline-panel {
padding: 0 100px 20px 20px
}
.timeline>li .timeline-image {
color: black;
}
.timeline:before {
background-color: black;
}
<!DOCTYPE html>
<html lang="en">
<head>
<title>Advising WebApp</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.0/jquery.min.js"></script>
<script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="main.css">
</head>
<header>
<div class="container ">
<div class="well">
<div id="profile">
<b id="welcome"><i><?php echo $login_session; ?></i></b>
<b id="logout"> <span class="glyphicon glyphicon-log-out"></span> Log-out</b>
<!-- <b id="logout">Log Out</b> -->
</div>
<h1>Advising WebApp</h1>
<p> Web App that helps with advising of CS majors!</p>
</div>
</div>
</header>
<body>
<div class="container">
<div class="row">
<div class="col-lg-12 text-center">
<hr class="light">
</div>
</div>
<div class="row" id="about-affects">
<div class="col-lg-12">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
</div>
</div>
<section id="mustTake">
<div class="container-fluid">
<div class="row no-gutter">
<div class="col-lg-12 text-center">
<h2 class="section-heading">MUST TAKE ALL</h2>
<hr class="primary">
</div>
<div class="col-xs-6 col-md-3">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
<div class="col-xs-6 col-md-3">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
<div class="col-xs-6 col-md-3">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
<div class="col-xs-6 col-md-3">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
</div>
</div>
</section>
<script src="../projectclass/js/main.js" type="text/javascript"></script>
</body>
</html>

Answer 1

The total of col-xs-* col-md-* col-sm-* must be 12 per class="row" you are exceding that number.
Try with this:
<section id="mustTake" >
<div class="container-fluid">
<div class="row no-gutter">
<div class="col-lg-12 text-center">
<h2 class="section-heading">MUST TAKE ALL</h2>
<hr class="primary">
</div>
</div>
<!-- Mobile -->
<div class="row">
<div class="col-xs-6 hidden-md hidden-lg">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
<div class="col-xs-6 hidden-md hidden-lg">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
</div>
<div class="row">
<div class="col-xs-6 hidden-md hidden-lg">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
<div class="col-xs-6 hidden-md hidden-lg">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
</div>
<!-- Desktop -->
<div class="row">
<div class="col-md-3 hidden-sm hidden-xs">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
<div class="col-md-3 hidden-sm hidden-xs">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
<div class="col-md-3 hidden-sm hidden-xs">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
<div class="col-md-3 hidden-sm hidden-xs">
<ul class="timeline">
<li>
<div class="timeline-image">
<h4>CPS210-CompSci-I </h4>
</div>
</li>
<li>
<div class="timeline-image">
<h4>CPS310-CompSci-II</h4>
</div>
</li>
</ul>
</div>
</div>
</div>

Answer 2

In your Id mustTake you have exceeded total numbers of cols per row (i.e. 12). For each row class you have 12 cols that you can use (Bootstrap grid system): http://www.w3schools.com/bootstrap/bootstrap_grid_basic.asp