JSFiddle - React, Tailwind, and code Playground

HTML

<div class="all">
  <div class="content">
    <div class="content__part">
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Ad fugit, voluptates, culpa sunt quo inventore neque nesciunt fugiat odio quas fuga repudiandae dicta optio accusamus odit, provident expedita eos quod.
    </div>
    <div class="content__part">
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Ad fugit, voluptates, culpa sunt quo inventore neque nesciunt fugiat odio quas fuga repudiandae dicta optio accusamus odit, provident expedita eos quod.
    </div>
  </div>
  <div class="sidebar">
    Lorem ipsum dolor sit amet, consectetur adipisicing elit. Ad fugit, voluptates, culpa sunt quo inventore neque nesciunt fugiat odio quas fuga repudiandae dicta optio accusamus odit, provident expedita eos quod.
  </div>
</div>

CSS

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

.sidebar {
  float: left;
  width: 300px;
  min-height: 500px;
  background: #333;
  padding: 15px;
  font-size: 16px;
}

.content {
  float: right;
  width: calc(100% - 300px);
  min-height: 500px;
  background: #eee;
  font-size: 0;
}

.content__part {
  display: inline-block;
  width: 50%;
  padding: 15px;
  font-size: 16px;
}

@media only screen and (max-width : 768px) {
  .content__part {
    display: block;
    width: 100%:
  }
}