Checkbox acceptance privacy in working contact form

Good morning,
I wanted to ask a question about the fast contact page of my site.
I had inserted the phrase but in fact the checkbox was not working (Surely my skills in php are not enough ...).

What changes / additions are needed in the file template.contact.php to insert between "send copy to your email" and "recaptcha" a phrase acceptance privacy policy with chekbox working?
Thank you very much if you can help me!

Hello,

Adding additonal fields into default contact form requires modifications of the template.contact.php file. Unfortunately this kind of modifications are beyond our technical support, if you want to have custom fields, please use 3rd party plugin, i.e. Contact Form 7.

Ok, thanks!
Regards