Adding custom fields

Hi everyone,

I’m new to contact form 7 and would ideally like to use it with these fields:

<div class="dfd-contact-from-style-3">

<p class="dfd-half-size dfd-border-bottom dfd-border-right">[text* first-name placeholder "First Name"]</p>
<p class="dfd-half-size dfd-border-bottom dfd-border-right">[text* last-name placeholder "Last Name"]</p>

<p class="clear"></p>

<p class="dfd-half-size dfd-border-bottom dfd-border-right">[text* company-name placeholder "Company Name"]</p>
<p class="dfd-half-size dfd-border-bottom">[email* company-email placeholder "Company Email"]</p>

<p class="clear"></p>

<p class="dfd-half-size dfd-border-bottom dfd-border-right">[text* phone-number placeholder "Company Phone Number"]</p>
<p class="dfd-half-size dfd-border-bottom">[email mobile-number placeholder "Mobile Phone Number"]</p>

<p class="clear"></p>

<p class="dfd-border-bottom">[textarea* additional-info placeholder "Additional Information or Questions"]</p>

<p>[submit "SEND MESSAGE"]</p>
</div>

Can anyone tell me why it doesn’t work?

https://wordpress.org/plugins/contact-form-7/