Here is how to change the setting if you do not want a notification every time you create an event.
1. Open the app's Settings screen and tap [General settings].
2. Tap [Normal event reminder] and [All-day event reminder] at the bottom.
3. Tap each checkmark to clear it, so that none remain selected.
After this, newly created events have no notification set, so notifications no longer arrive.
When you do want a notification, you can set one while creating the event.
Thank you.