<div class="wrapper">
      <div class="first-box">
      <h2 class="heading">Box 1 </h2>
            
      <div class="one">Item One</div>
      <div class="two">Item Two</div>
      <div class="three">Item Three</div>

        </div>

        <div class="second-box">
            <h2>Box 2 </h2>
        </div>

        <div class="third-box">
            <h2>Box 3 </h2>
        </div>

        <div class="fourth-box">
            <h2>Box 4 </h2>
        </div>

        <div class="fifth-box">
            <h2>Box 5 </h2>
        </div>

        <div class="sixth-box">
            <h2>Box 6 </h2>
        </div>
    </div>

.wrapper{
    background-color: gainsboro;
    display:grid;
    border: 1.5px black solid;
    grid-template-columns: repeat(3, 1fr);
    grid-auto-rows: 100px;
    column-gap: 7px;
    row-gap: 1.5em;
}

.first-box{
    padding: 10px;
    border: 1px black solid;
    text-align: center;
    background-color:seashell;
    grid-column-start: 1;
    grid-column-end: 4;
    grid-row-start: 1;
    grid-row-end: 3;
    display:grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 3px;
}
.first-box .heading{
    grid-column-start: 1;
    grid-column-end: 4;
}
.first-box .one{
    border: 1px black solid;
    padding: 5px; 
    background-color:ivory;
}

.first-box .two{
    border: 1px black solid;
    padding: 5px; 
    background-color:ivory;
}
.first-box .three{
    border: 1px black solid;
    padding: 5px; 
    background-color: ivory;
}

.second-box{
    padding: 10px;
    border: 1px black solid;
    text-align: center;
    background-color:beige;
    grid-column-start: 1;
    grid-row-start: 3;
    grid-row-end: 5;
}

.third-box{
    padding: 10px;
    border: 1px black solid;
    text-align: center;
    background-color:oldlace;
}

.fourth-box{
    padding: 10px;
    border: 1px black solid;
    text-align: center;
    background-color: linen;
}

.fifth-box{
    padding: 10px;
    border: 1px black solid;
    text-align: center;
    background-color: lavenderblush;
}

.sixth-box{
    padding: 10px;
    border: 1px black solid;
    text-align: center;
    background-color: mistyrose;
}