2-way synchronization between iCal and Google Cal

Greetings RobertoMPS,

Welcome to Apple Support Communities. You. can add your Google account to the Calendar app on your iMac to sync the calendars. Follow the steps per the Apple Support article: Access iCloud, Google, and other calendars in Calendar on Mac - Apple Support

"Add an account

• Choose Calendar > Add Account, select the account type, then follow the onscreen instructions.
• For information about adding an iCloud account, see Set up iCloud on your Mac. For information about adding other accounts, see Add an account.
• Set up your iOS devices to use the same account, so that your calendars stay up to date across all those devices and your Apple Watch. For more information, see the “Get started” section of the user guide for iPhone, iPad, or iPod touch. For a device that doesn’t use the latest iOS version, get the user guide from the Apple Support manuals website.

Each account you add is listed separately in the sidebar. If the sidebar isn’t showing, choose View > Show Calendar List or click Calendars in the toolbar."

Feel free to reach back out if you have any questions.

Best regards!