// Hello Gabriella

// What is the difference with inline styling vs css styling

// This was what you used for your images:

<div class="lala" style="background: 'your_image'"></div>
// This would add a image to your page, however the height, width isnt set, so when we resize the browser the image will start repeating.

// A better way to solve this if you wish to add a background to a section, such as about/contact/faq etc is:
// This is just exampe code
<div class="about">
  <div class="container">
    <div class="row">
      <div class="col-md-4"></div>
    </div>
  </div>
</div>

// Then in your style css

.about{
background-image: url('your_image');
background-size: cover;
height: your height here, i suggest looking at what VH and VW is for css, or you can set a fixed height in px or %;
}