This is due to CSS styling applied to standard HTML form elements within your current WordPress theme.
In particular the following code?? https://www.fansclubchievo.it/wp-content/themes/hueman/style.css:
.wpcf7 input[type="text"], .wpcf7 input[type="email"] {
display: block;
float: left;
padding: 10px;
width: 100%; /* THIS CODE */
}
Also:
.themeform input[type="text"], .themeform input[type="password"], .themeform input[type="email"], .themeform textarea {
background: none repeat scroll 0 0 #fff;
border: 2px solid #ddd;
color: #777;
display: block;
max-width: 100%; /* THIS CODE */
outline: medium none;
padding: 7px 8px;
}
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.??