The CSS 'order' property within a 'display:flex;' parent container will allow you to adjust the display order of items inside the container. https://www.w3schools.com/cssref/css3_pr_order.asp
Assuming you had some HTML like this (where the content comes before the form in the document):
<div style="display:flex;">
<div class="contentElement">Some content here</div>
<div class="mktoForm" id="Form" mktoName="Form"></div>
</div>
You can then use some responsive breakpoints and do something mobile-first in CSS like:
/* this will stack the form ABOVE the content */
div.mktoForm {order:0;}
div.contentElement {order:1;}
/* this will reverse the display order for tablet and desktop displays */
@media screen and (min-width:768px) {
div.mktoForm {order:2;}
div.contentElement {order:1;}
}