Hi Thiago, 🙂
For more about the registration form, please read the following posts:
Please be aware that the register fields are managed by BuddyPress plugin. In case you need more help with this, it’s best if you try to reach the plugin authors. They will be more informed and better suited to help you.
To go further, we invite you to post your request on their support forums: BuddyPress support.
We remain available for all support requests related with the use of your theme.
Best,