After a lot of testing I found out that the error is basicly solved by setting the correct Calendar ID for the google calendar. Because google calendar uses either an ID like your gmail address or if you have more calendars synchronized inside of your google calendar the calendar ID is called after the list of different ID's.
The main cause in my code was a Capital use inside the word "primary". It looks like the google calendar ID is Capital sensitive! This solved the half of my code. If you get alarm 404 with everything worked out properly. You should first look after the declaration of the word "primary" without capitals.
Than I looked after the code 403. This was caused by the EVENT_ID from google Calendar.
In several examples everybode tells you that you need to use:
If you look at the google.calendar.API.v3 documentation you will see that the eventID must be an unique ID from 5 up to 32 Characters/numbers. The system.guid.newguide.tostring will give you a ID with 32 chars, but will make sequences of xxxxxxxx-xxxxxxxx-xxxxxxxx-xxxxxxxxx.
The only thing you need to do before the event ID is accepted by Google Calendar without giving you an error is:
Hope this will help anybody who also wants to work with Google Calendar API in vb.net