Hello again José,
For the purchase of tickets I need that it is mandatory that the user registers, is this possible?
The short answer is yes.
But this will also depend on what you mean by registering (answer a few questions or provide attendee information is the most common definition, other simply want users to create an account).
Either way, we have you covered.
To do this you will need to grab a copy of our Event Tickets Plus premium add-on: https://theeventscalendar.com/product/wordpress-event-tickets-plus/
Let me know if that helps.
Have a great day!
Geoff B.