How to fix incorrect work of Contact Form 7 on a ready theme?

Question

WordPress

I screwed up a site on the topic, but it turns out that it has jambs and an obvious one is a sur with a contact form (Contact Form 7 plugin) .
When you try to send a message (it comes to the addressee) - nothing happens for the user, namely, the form itself is not folded and the message does not give any. BUT in fact, the message is displayed under the footer, but you won’t notice it in any way and the user will be confused.
By going to the demo of this theme and using the "GET A QUOTE" form in the header, you can project this problem. Please tell me how to fix this bug