Splanner and calendar events duplicated

Hello,

I have a Samsung Galaxy Note LTE and have the following issue.

I have just 1 gmail account. I receive 2 notifications when I receive an email and 2 of the same events are displayed in the Splanner if it's a meeting.
How do I prevent this? I want just one notification and one calandar entry.
The gmail app is running as well however if I try removing the account it tells me that I will lose all contacts etc on the phone.

Any advice?

Thanks