Shape 5

We tried to set the smtp settings with Wp-mail-smtp plugin so the quick contact sends email via smtp.
The function is not working.
And how to correctly set up the plugin.

I recommend making sure you're using the most recent download of the plugin.

The currently released version of the plugin uses the wp_mail function, and it worked fine in testing, so if you've done something to change the way wp_mail works, any issues you are having are most likely caused by the third-party plugin, which as per the Shape 5 Terms of Use (http://www.shape5.com/terms_of_use.html), is not covered by support.

As for setting up the plugin, all you need to do is install it and activate it; once that's done, the widget will be available to place in any widget position, and you'll just need to configure the form using the settings on the widget.

Thank you. It worked well now.
Can you tell/teach me how to redirect to a page e.g. /thank-you.html after the form is submitted.

Thank you very much.

There is no option to redirect after submitting the form, but the text options for the widget will allow you to customize the thank you message displayed by the widget when the form is submitted.