<style>
/* Stack all webform fields full-width on this page */
.webform-ajax-form-wrapper .col-6,
.webform-submission-form .col-6 {
    flex: 0 0 100% !important;
    max-width: 100% !important;
    width: 100% !important;
}

.webform-ajax-form-wrapper input,
.webform-ajax-form-wrapper textarea,
.webform-ajax-form-wrapper select,
.webform-submission-form input,
.webform-submission-form textarea,
.webform-submission-form select {
    width: 100% !important;
    box-sizing: border-box !important;
}
</style>