Hi Gisella,
Thanks for reaching out! At the moment, there is no way to change the base URL slug depending on the category of events that is being displayed. However, you can select a URL slug to be shared across all of your event types, then link to each event category to display a calendar with only events from that category. An example of a category-specific calendar can be seen here on our WP Shindig demo site:
http://wpshindig.com/events/category/wp-meetups/
For more information on event categories and how to work with them, you can check out our Knowledgebase article below! I’d also be glad to answer any specific questions you might have about how to use categories on your site. 🙂
https://theeventscalendar.com/knowledgebase/event-categories/
I hope that helps to get you on your way here! Thanks again, and let us know if you should have any other questions!