Do I have to manually transfer the “normal” data to big data otherwise I hit the 100.000 rows limit again at one point?
Yes, you have to manually transfer the data at this moment. In version 3.5, you can set a rule to automatically transfer the data every time at specific hour.
And in my “big data view” I will see normal (limited) & archived (unlimited) elements, right?
Yes.
Is there a (hidden) API to create the big data views? could only find this for normal views
The document for the API will be updated in version 3.4.
Is there a (hidden) API or automation to move the rows from “normal” to “archive/big data”
There is such an API, but with the automation rule, you don’t need such an API.