Formidable forms are not responsive by default. However, it can easily be done if you add the following to the Form’s or View’s custom CSS or you can add it to the entire site.
@media only screen and (max-width: 600px) {
.frm_grid_container .frm3,.frm_grid_container .frm6, .frm_grid_container .frm9,.frm_grid_container .frm4{
grid-column: span 12 / span 12 !important;
}
}You can learn more about grid layout using the following link
https://www.w3schools.com/cssref/tryit.php?filename=trycss_grid-column2