In the past few years, we have covered plenty of plugins that let you integrate Google Calendars into WordPress. Private Google Calendars is also worth a look. It lets you display private and public Google Calendars with a shortcode, block or widget.
This plugin lets you access private and public calendars using OAuth2 or an API key. It also uses caching to improve performance. Users can filter public and private calendar events with a click. You can use the pgc shortcode and customize it using various attributes.