Keeping the modal open and display the TY message after form fillout

Dear all,

This is what we are trying to achieve:

On a click on a button, a modal form pops up. The form contains a text that will be the future thank you message. The reason the TY message is in the form is because this is the only element that the Marketo users can access.

The whole is to be embedded on a web site, not on a Marketo LP

On form success, we want to copy the thank you message and have it to replace the form in the modal zone and keep it displayed for a while (for example 5 seconds) before the modal window disappears.

So far, we have been able to do almost everything, excepted that the modal shuts down immediately.

Any idea ?

Here is a test page:

https://digital-solutions2.konicaminolta.fr/02-CFM-Contact-Configurateur_test.html

-Greg