Open drop-down menu after hover (CSS)

Question

I created a horizontal menu, which, when you hang up an item, a drop-down menu appears. Everything is fine. However, when you leave the menu item (to use the drop-down list), the drop-down menu disappears. I understand that this is because you no longer parry it, but how can I solve it? Note. I don’t want the dropdown menu to be directly below it, I want a reasonable gap between the menu item and the dropdown (as I have at the moment). Thank.

HTML

<header id="header">
    <div class="container">
        <a href="#top-anchor"><div id="logo"></div></a>
        <nav class="header-menu">
            <a href="index.html" class="header-menu-item">ABOUT</a>
                <div class="about-dropdown">
                    <a href="index.html#core-services-anchor">CORE SERVICES</a>
                    <a href="index.html#atandl-anchor">AT&amp;L</a>
                    <a href="index.html#hseq-anchor">HSEQ</a>
                    <a href="index.html#clients-anchor">CLIENTS</a>
                    <a href="index.html#contact-anchor">CONTACT</a>
                </div>
            <a href="services.html" class="header-menu-item">SERVICES</a>
            <a href="facilities.html" class="header-menu-item">FACILITIES</a>
            <a href="#map-anchor" class="header-menu-item">CONTACT</a>
        </nav>
        <div id="hamburger"></div>
        <!--<div id="box-shadow-menu"></div>-->
    </div>
</header>

CSS

#header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100px;
  user-select: none;
  display: block;
  transition: all 0.8s;
  line-height: 100px;
  z-index: 1000;
  transform: translateX(0);
  backface-visibility: hidden;
  margin: 0;
}

header .container {
  width: 1440px;
  height: 100px;
  border-bottom: 0.75px solid rgba(255,255,255,0.1);
}

#logo {
  width: 55px;
  height: 55px;
  float: left;
  margin-top: 27px;
  background-image: url(../images/logo_white.png);
  background-size: cover;
}

nav.header-menu {
  float: right;
  height: 96px;
  vertical-align: middle;
  padding-top: 1px;
}

.header-menu-item {
  font-family: 'Montserrat', sans-serif;
  font-size: 11px;
  font-weight: 800;
  margin-left: 20px;
  text-decoration: none;
  color: #ffffff;
  line-height: 96px;
  letter-spacing: 0.5px;
  transition: 0.55s;
}

.toggle {
  opacity: 0.3;
}

.current {
  border-bottom: 2px solid #fff;
  padding-bottom: 40px;
}

.about-dropdown {
  position: absolute;
  background-color: #fff;
  min-width: 160px;
  box-shadow: 0 0 4px 3px rgba(0,0,0,0.1);
  z-index: 3000;
  margin-top: 35px;
  margin-left: -35px;
  border-radius: 3px;
  display: none;
  transition: 0.8s;
}

.about-dropdown a {
  display: block;
  text-decoration: none;
  padding: 0px 28px;
  font-family: 'Montserrat', sans-serif;
  font-size: 11px;
  font-weight: 800;
  margin: 0;
  line-height: 50px;
  border-bottom: 1px solid rgba(0,0,0,0.1);
}

.header-menu-item:hover + .about-dropdown {
  display: block;
}

Answer 1

'a' . 'a', , , .

-

.about-dropdown a:hover {
    padding-bottom: 30px; /*height dependent on the gap you want to fill*/
    position: absolute; 
}

Answer 2

, . CSS.

, . , . , , 1 . , . , , , .

.trigger {
  box-sizing: border-box;
  position: relative;
  width: 120px;
  margin: 0 0 50px;
  padding: 10px;
  background: #bada55;
  text-align: center;
}

.sub {
  box-sizing: border-box;
  position: absolute;
  top: 100px;
  left: 0;
  width: 120px;

  background: #4863a0;
  color: #fff;
  text-align: left;
  
  /* hide element for now */
  max-height: 0; overflow: hidden;
  opacity: 0;
  /* make submenu not hoverable when opacity transition finished,
   * do this instantaneously */
  transition: max-height 0s 1.5s,
              /* hide the submenu after 1 second, in 400ms */
              opacity .4s 1s;
  
  /* prevent users from showing submenu when hovering hidden element */
  pointer-events: none;
}

/* sub elements can be hovered */
.sub > * {
  pointer-events: auto;
}

/* show submenu when trigger or menu itself is hovered */
.sub:hover,
.trigger:hover .sub {
  max-height: 500px;
  opacity: 1;
  transition-delay: 0s;
}

/* give items some spacing */
.item:not(:last-child) {
  padding: 10px 10px 5px;
}
.item:last-child {
  padding: 10px;
}

<div class="trigger">HOVER ME
  <div class="sub">
    <div class="item">Item 1</div>
    <div class="item">Item 2</div>
    <div class="item">Item 3</div>
    <div class="item">Item 4</div>
  </div>
</div>

Hide result

, (ab) CSS . , . , , . , , . , , . , (max-height: 0) (overflow: hidden). hover, , pointer-events: none. , , max-height. , , , pointer-events: auto . , max-height: none, , 500px .