Stop iPhone calendar from reading my google calendar

I have a company iPhone and the apple Calendar is used for professional appointments. As I use the iPhone in my private life as well, I have Google calendar on it which I use for everything except work.

The iPhone calendar automatically takes over all entries in Google calendar and I do not want this. I've already turned those items off in the calendar view, but I still get the warnings twice (google and apple calendar).

I think I've found how to turn those warnings off in the apple Calendar now too, so that part is solved.

But in general, I do NOT want the iPhone to access my google calendar and take it into its own. How do I stop this?

When I click on one of my google agenda's in the Apple calendar and delete it, it reappears in the list again 2sec later and is also checked as visible. So there's an active sync going on but I can't for the life of me find where to turn it off...

Thanks!