CSS organization with BEM
Well, if you are using Bootstrap, you should not alter the classes that Framework is using, like navabar for example.
The basic with BEM is that you should chain classes in a way to create a meaningful hierarchy, like in a component, where you have an object that contains everything else. Like that you leverage SASS nesting to create a component-like structure.
For example:
&lt;header&gt;

  &lt;navbar class=&quot;navigationBar navbar&quot;&gt;
    &lt;div class=&quot;container&quot;&gt;
      &lt;div class=&quot;navigationBar--logo&quot;&gt;&lt;/div&gt;
        &lt;ul class=&quot;navigationBar--navigation&quot;&gt;
          &lt;li class=&quot;navigationBar--navigation--item&quot;&gt;
            &lt;a class=&quot;navigationBar--navigation--item--link&quot; href=&quot;#&quot;&gt;Item-1&lt;/a&gt;
            &lt;a class=&quot;navigationBar--navigation--item--link&quot; href=&quot;#&quot;&gt;Item-2&lt;/a&gt;
            &lt;a class=&quot;navigationBar--navigation--item--link&quot; href=&quot;#&quot;&gt;Item-3&lt;/a&gt;
          &lt;/li&gt;
        &lt;/ul&gt;
      &lt;/div&gt;
    &lt;/div&gt;
  &lt;/navbar&gt;

 &lt;section class=&quot;content&quot;&gt;
    &lt;div class=&quot;container&quot;&gt;
      &lt;div class=&quot;content--heading--primary&quot;&gt;
        &lt;span class=&quot;content--heading--primary--main&quot;&gt;Welcome To Our Studio!&lt;/span&gt;
        &lt;span class=&quot;content--heading--primary--sub&quot;&gt;It's Nice To Meet You&lt;/span&gt;
     &lt;/div&gt;
   &lt;/div&gt;
 &lt;/section&gt;

&lt;/header&gt;

In this case the SASS will be:
.navigationBar {
    width:104px;
  
    &amp;--logo { width:103px; }
    &amp;--navigation {
      width:102px;
      
        &amp;--item {
          width:101px;
          
            &amp;--link {width:100px; } 
        }
    }
}


.content {
  width:100px;
  
  &amp;--heading--primary {
    width: 101px;
    
    &amp;--main { width: 102px; }
    &amp;--sub { width: 103px; }
  }
}

Check the SASS code with SassMeister (https://www.sassmeister.com) to see how it turns to CSS