Follow the steps below to hide calendars and/or categories:

Tap on settings
Tap on My Calendars
Tap on any check mark beside each calendar title to hide it from your calendar views.

Tap on the arrow beside the calendar name (on the left) to reveal your categories. Tap on the check mark to hide.

Tap DONE to save your settings.
The calendars/categories in which you removed the check mark will now be hidden from your calendar views.