Вы можете сделать это так.
.main_container {
display: grid;
grid-template-columns: auto auto;
grid-row-gap: 30px;
grid-column-gap: 30px;
}
.sections {
height: 200px;
text-align: center;
background-color: aqua;
}
/*here for mobiles inside mobile media query put this*/
.main_container {
display: grid;
grid-template-columns: auto;
grid-row-gap: 30px;
grid-column-gap: 30px;
}
<div class="main_container">
<div class="sections">A</div>
<div class="sections">B</div>
<div class="sections">C</div>
<div class="sections">D</div>
</div>