Blocks are floating on each other. Bootstrap - html

Question

Good day. Tell me please. Taught django, and took the template html, css, js. There is used bootstrap. Few adapted it for myself. He worked on a 17 '' monitor. Actually, when the 21 'monitor began to look, the blocks ran over each other. Besides, on 15'6, through the phone everything is in order. Tried to attribute in addition to col-sm as col-lg - the result did not. Tell me, please, how can I solve this problem.
It should be - https://i.stack.imgur.com/usEMI.png
How it happened - https://i.stack.imgur.com/UvUfX.png
Right-sidebar code:
<div class="col-md-9 col-lg-9">
<div class="col-md-12 col-lg-12 page-body">
<div class="row">
<div class="sub-title">
<h2>Some Notes</h2>
<i class="icon-envelope"></i>
</div>
<div class="col-md-12 col-lg-12 content-page">
<div class="col-md-12 col-lg-12 blog-post">
<div class="post-title">
<h1>джанго код</h1>
</div>
<div class="post-info">
<span>джанго код / by джанго код</span>
</div>
<p style="word-break: break-all"> джанго код</p>
<span>Read More</span>
</div>
<div class="col-md-12 col-lg-12 text-center">
Load
<div id="post-end-message"></div>
</div>
</div>
</div>
Left-sidebar code:
<div id="main">
<!-- about(left sidebar) -->
<div class ="col-md-3 col-lg-3">
<div class="about-fixed">
<div class="my-pic">
<img src="{% static 'images/pic/av-pic.png' %}" alt="av-pic">
</div>
<div class="my-detail">
<div class="white-spacing">
<h1></h1>
<span>Learning Web Development</span>
</div>
<ul class="social-icon">
<li><i class="fa fa-github"></i></li>
<li><i class="fa fa-vk"></i></li>
</ul>
</div>
P.S. Sorry for english.