Style a contact form 7 to seems like Divi Theme Contact style

contact-form-7-format-to-style-divi-theme.css

/*contact form 7 like Divi theme */

/*  fields. Note "assunto" field, is explained in Select section of this file */
.wpcf7-text, .wpcf7-textarea, .wpcf7-captchar, .assunto{
  background-color: #eee !important;
  border: none !important;
  width: 100% !important;
  -moz-border-radius: 0 !important;
  -webkit-border-radius: 0 !important;
  border-radius: 0 !important;
  font-size: 14px;
  color: #999 !important;
  padding: 16px !important;
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
}

/* submit button */
.wpcf7-submit {
  margin: 8px auto 0;
  cursor: pointer;
  font-size: 20px;
  font-weight: 500;
  -moz-border-radius: 3px;
  -webkit-border-radius: 3px;
  border-radius: 3px;
  padding: 6px 20px;
  line-height: 1.7em;
  background: transparent;
  border: 2px solid;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  -moz-transition: all 0.2s;
  -webkit-transition: all 0.2s;
  transition: all 0.2s;
}

.wpcf7-submit:hover { 
  background-color: #eee; 
  border-color:#eee; 
  padding: 6px 20px !important; 
}

/*bold label*/
.wpcf7-form label {font-weight:bold}

/* select: put a class, and call by class. In this example, my field class is: "assunto" */
.assunto {display:block}
.assunto .wpcf7-select {
  border:none; background:transparent; width:100%; font-size: 14px;
  color: #999 !important;
}
/* end select */

/* radio button: put a class, and reference that class. Ex.: my radio button field class is: "radio-class"'
.radio-class .wpcf7-radio {display:table;}
span.wpcf7-list-item { display: table-row; }
span.wpcf7-list-item * { display: table-cell; padding-right:30px;}
/* end radio button */