Show / Hide (Toggle) submenus of a navigation menu using jquery doesnt work as expected

I created a single horizontal menu using CSS, HTML and jquery. When someone clicks on a menu item then it displays a sub-menu.

My problem is that when a submenu is already open and I click on another menu item then it shows the new submenu but it doesn't hide the previous menu which is already open.

UPDATE: I edited the question so now is focused on one problem only.

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

$(".menus_li").click(function(e) {
  $(".blocks_ul", this).toggleClass('submenu-is-active');
});

<!-- language: lang-css -->

a {
  color: #fff;
  text-decoration: none;
}

li {
  list-style: none;
}

.top-menu {
  z-index: 2;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  display: flex;
  width: 100%;
  background: #0088ff;
  padding: 1rem;
  margin: 0;
}

.menus_li {
  font-weight: bold;
  margin-left: 1rem;
}

.blocks_ul {
  display: none;
  position: absolute;
  background: #fff;
  top: 100%;
  min-width: 120px;
  border-radius: 8px;
  padding: 1rem;
}

.blocks_ul a {
  color: #000;
}

.blocks_ul li {
  padding-left: 10px;
  font-weight: normal;
  padding: 0.4rem 0.7rem;
}

.blocks_ul.submenu-is-active {
  display: block;
}

.bg_submenu {
  background-color: rgba(0, 0, 0, 0.6);
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 1;
  display: none;
}

.bg_submenu.show {
  display: block;
}

<!-- language: lang-html -->

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<div class="bg_submenu"></div>
<ul class="top-menu">
  <li class="menus_li"><a href="#">Cars +</a>
    <ul class="blocks_ul">
      <li><a class="menu-link" href="#">Mercedes</a></li>
      <li><a class="menu-link" href="#">Jeep</a></li>
      <li><a class="menu-link" href="#">Ford</a></li>
      <li><a class="menu-link" href="#">BMW</a></li>
      <li><a class="menu-link" href="#">Tesla</a></li>
    </ul>
  </li>
  <li class="menus_li"><a href="#">Computers +</a>
    <ul class="blocks_ul">
      <li><a class="menu-link" href="#">Apple</a></li>
      <li><a class="menu-link" href="#">Lenovo</a></li>
      <li><a class="menu-link" href="#">HP</a></li>
      <li><a class="menu-link" href="#">Dell</a></li>
      <li><a class="menu-link" href="#">Acer</a></li>
    </ul>
  </li>
</ul>

<!-- end snippet -->

You can change your code as follows (comments in code)

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

const $blocks = $(".blocks_ul");       // get all blocks
const $background = $(".bg_submenu");  // get background

$(".menus_li").on('click', e => {
  const $thisBlock = $(".blocks_ul", e.currentTarget);      // get current block

  $blocks.not($thisBlock).removeClass('submenu-is-active'); // remove class from other blocks
  $thisBlock.toggleClass('submenu-is-active');              // toggle the class on the current block
  $background.toggleClass('show', $thisBlock.hasClass('submenu-is-active')); // only show the background if you are showing the block
});

$('body').on('click', e => {
  const $clicked = $(e.target);  // get the target that was clicked
  
  // check if the click originated in the menu
  if (!$clicked.hasClass('menus_li') && !$clicked.closest('.menus_li').length) {
    // if not do the following
    $blocks.removeClass('submenu-is-active'); // hide menu
    $background.removeClass('show'); // hide background
  }
})

<!-- language: lang-css -->

a {
  color: #fff;
  text-decoration: none;
}

li {
  list-style: none;
}

.top-menu {
  z-index: 2;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  display: flex;
  width: 100%;
  background: #0088ff;
  padding: 1rem;
  margin: 0;
}

.menus_li {
  font-weight: bold;
  margin-left: 1rem;
}

.blocks_ul {
  display: none;
  position: absolute;
  background: #fff;
  top: 100%;
  min-width: 120px;
  border-radius: 8px;
  padding: 1rem;
}

.blocks_ul a {
  color: #000;
}

.blocks_ul li {
  padding-left: 10px;
  font-weight: normal;
  padding: 0.4rem 0.7rem;
}

.blocks_ul.submenu-is-active {
  display: block;
}

.bg_submenu {
  background-color: rgba(0, 0, 0, 0.6);
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 1;
  display: none;
}

.bg_submenu.show {
  display: block;
}

<!-- language: lang-html -->

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<div class="bg_submenu"></div>
<ul class="top-menu">
  <li class="menus_li"><a href="#">Cars +</a>
    <ul class="blocks_ul">
      <li><a class="menu-link" href="#">Mercedes</a></li>
      <li><a class="menu-link" href="#">Jeep</a></li>
      <li><a class="menu-link" href="#">Ford</a></li>
      <li><a class="menu-link" href="#">BMW</a></li>
      <li><a class="menu-link" href="#">Tesla</a></li>
    </ul>
  </li>
  <li class="menus_li"><a href="#">Computers +</a>
    <ul class="blocks_ul">
      <li><a class="menu-link" href="#">Apple</a></li>
      <li><a class="menu-link" href="#">Lenovo</a></li>
      <li><a class="menu-link" href="#">HP</a></li>
      <li><a class="menu-link" href="#">Dell</a></li>
      <li><a class="menu-link" href="#">Acer</a></li>
    </ul>
  </li>
</ul>

<!-- end snippet -->