Even if Event Alerts is enabled, there may still be some settings on your phone that prevent Calendar from reminding you of your schedule. I recommend checking the following items.
1.Go to Settings -> Calendar -> Default Alert Times. Ensure that the alert times for Birthdays, Events and All-Day Events are set to your preferences.
2.Go to Settings -> Notifications-> Calendar. Check if Allow Notifications is toggled on.
3.Go to Settings -> Focus -> Do Not Disturb. Ensure that Do Not Disturb or any other Focus mode that might silence notifications is turned off, or configure exceptions to allow Calendar alerts.
Finally, to ensure nothing is missed, you can open the Calendar and then tap on "Calendar" at the bottom of the screen. All events will be displayed. Then tap the "i" icon and ensure that Event Alerts are enabled for each event.