How to make a div appear below another div in CSS

Question

I have two divs nested inside a div called .content. In it I have an img.png and I want another div with some boxes inside it which will be below the img.png

<div class="navBox">
            <a href="#contact">/*Contact information*/</a>
        </div>
        <div class="navBox">
            <a href="#expertise">/*Expertise*/</a>
        </div>
        <div class="navBox">
            <a href="#projects">/*projects*/</a>
        </div>

Also, I tried every possible combination of positioning, padding, margins, but not z-index (not sure how to use it) and didn't get good results.

Thanks in advance.

*Edit: I managed to use other distribution methods.

.mainBox{
    position: relative;
    display: flex;
    width: 95%;
    height: 25vh;
    padding-top: 5vh;
    justify-content: space-evenly;
    align-items: left;
    vertical-align: middle;
}

.navBox{
    padding-top: 25px;
    padding-left: 10px;
    padding-right: 10px;
    width: 20%;
    height: 20vh;
    text-align: center;
    top: 50%;
    background: transparent;
}

.navBox a:hover{
    padding-top: 50%;
    background: transparent;
    color: var(--text-color);
    text-decoration: none;
    
}

a:visited, a:active, a:link{
    text-decoration: none;
    color: var(--text-color);
}

.navBox a{
    vertical-align: middle;
    color: var(--text-color);
    padding-top: 0.5rem;
}

Answer 1

Next time please share your code instead of screenshots, anyway, here is a sample code that does not use z-index

HTML

<div class="container">
  <div class="your-image">&nbsp;</div>
  <div class="your-boxes">&nbsp;</div>
</div>

CSS

.container {
  display: grid;
  grid-template-rows: 1 / 1;
  grid-template-columns: 1 / 1;
  justify-items: center;
  align-items: center
}

.your-image {
  background-color: red;
  width: 250px;
  height: 250px;
  grid-area: 1 / 1 / 1 / 1;
}

.your-boxes {
  background-color: green;
  width: 150px;
  height: 150px;
  grid-area: 1 / 1 / 1 / 1;
  justify-self: center;
}

Basically, you create a 1x1 grid and overlap two divs on the same column and row.

https://codepen.io/ChrisCoder9000/pen/NWMJdBo