With this approach i can merge / combine all my different calendar and generate a unified calendar.
Step 1: Select the primary calendar
Step2: Select "Share this Calendar"
Step 3: Make it public
Step4: Back to Calendar Settings and select HTML view
Step 5: Configuration tool ( Our Magic link )
Step6: Last step before you can publish a unified view.
If needed you can host this in your webserver as yourdomain.com/calendar.html