Add this to your .css:
@media only screen and (max-device-width: 480px) {
form.NewFromBlank_Default {
width: 100%;
}
form.NewFromBlank_Default div.formGroup {
display: block;
float: none;
}
form.NewFromBlank_Default label.sublabel {
float: none;
text-align: left;
}
form.NewFromBlank_Default div.columnGroup, form.NewFromBlank_Default textarea.formTextarea_Medium, form.NewFromBlank_Default input.formTextfield_Medium, form.NewFromBlank_Default select.formMenufield_Medium, form.NewFromBlank_Default div.wideColumnGroup,
form.NewFromBlank_Default input.formButton {
width: 100%;
box-sizing: border-box;
}
.Default-wrapper {
display: none !important;
}
form.NewFromBlank_Default span.buttonFieldGroup {
display: block;
float: none;
padding: 10px 0;
text-align: right;
}
}