The actual look of CF7 forms on your website will depend largely on the current WordPress theme used and the CSS styling that theme applies to standard HTML form elements.
To change the style of your CF7 forms you would need to edit the CSS style sheets used by your WordPress theme.
See Styling Contact Form for a general explanation of styling CF7 forms using CSS.
There is a link at the bottom of the page to a comprehensive and detailed article on Styling Contact Form 7 Forms. The article shows people, with suitable HTML & CSS skills, how to change the appearance of their Contact Form 7 Forms to meet their particular requirements.
I used firebug to examine your form and here the code that would correct the style of your form.
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Correction code:
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.wpcf7-form .wpcf7-textarea {
width: 425px;
}
.wpcf7-form .wpcf7-text {
width: 425px;
}
.wpcf7-form {
width: 425px;
margin: 0 auto;
}
Add your CSS via Child Theme or use custom CSS plugin.
You could also try the CF7 Skins plugin, saves time in styling Contact Form 7 forms