Layout Grid
Use the standard structure of .container or
.container-fluid, then .row, then
.col-* responsive columns.
col-4
col-4
col-4
<div class="container">
<div class="row">
<div class="col-12 col-md-6 col-lg-4">...</div>
<div class="col-12 col-md-6 col-lg-4">...</div>
<div class="col-12 col-md-12 col-lg-4">...</div>
</div>
</div>