How can I make my form disappear once the form has been completed and the success message pops up.
Give the form an ID. Make a script that removes the node of the ID or something like that when the form is submitted?
x = document.getElementById('formID');
Haven't tested it, but maybe this thing works out.
The success message appears with script disabled, so the decision is being made server side. Why not use the same condition to decide whether to render the form?