Here is how to create 2 columns in mobile view.

Step 1: Go to the decision tree scripts as shown in the image below.

Step 2: Click on the “Add” button under the Decision Tree Scripts.

Step 3: Add the code below
<style>
@media screen and (max-width: 767px) {
/* Make all containers display in a continuous flow */
.question-answers-groups.pure-g {
display: flex;
flex-wrap: wrap;
width: 100%;
}
/* Force each item to be exactly 50% width */
.question-answer-container.pure-u-1 {
width: 50% !important;
flex: 0 0 50%;
box-sizing: border-box;
}
/* Remove any margins that might be causing issues */
.question-answers-groups {
margin: 0;
}
/* Ensure items have consistent spacing */
.question-answer-outer {
margin: 5px;
}
/* Fix for the separate groups */
.question-mc {
display: flex;
flex-wrap: wrap;
}
.question-mc > .question-answers-groups {
display: contents; /* This makes children act as if they were direct children of parent */
}
}
</style>

Step 4: Save and publish.