For a project, I need to create the following footer

However like I said in the title, my footer's background-color neither take the full width or 'bottom' of the screen, there is a white space.
I tried to apply width:100% on footer but it doesn't work. I also tried to fiddle a bit with flexbox, but it was also fruitless.
Here is my code:
footer {
  display: flex;
  flex-flow: row wrap;
  justify-content: space-around;
  background-color: #F2F2F2;
  margin-top: 30px;
}
footer a {
  position: relative;
  right: 36px;
  color: black;
  text-decoration: none;
}
footer a:hover {
  color: #0065FC;
}
.footer-nav {
  display: flex;
  flex-flow: column wrap;
  list-style: none;
}
.footer-item {
  margin-top: 6px;
}
<footer>
  <nav>
    <h4>About</h4>
    <ul class="footer-nav">
      <li class="footer-item"><a href="#">Site Map</a></li>
      <li class="footer-item"><a href="#">General Terms and Conditions</a></li>
      <li class="footer-item"><a href="#">Data and Privacy</a></li>
    </ul>
  </nav>
  <nav>
    <h4>Our Accommodations</h4>
    <ul class="footer-nav">
      <li class="footer-item"><a href="#">Quality Assessments</a></li>
      <li class="footer-item"><a href="#">You have a hotel ?</a></li>
    </ul>
  </nav>
  <nav>
    <h4>Assistance</h4>
    <ul class="footer-nav">
      <li class="footer-item"><a href="#">Help Desk</a></li>
      <li class="footer-item"><a href="#">Contact Us</a></li>
    </ul>
  </nav>
</footer>
I thank in advance anybody who will take the time to help me.