Hi @Janosch1, welcome to the community!
That’s a good question and it’s related to this ongoing discussion - we are planning to properly scope how to handle project and site points for Revit and C3D and you can follow this issue on github if you’re interested!
For now, Civil3D elements are sent and received relative to the internal origin, while Revit elements are sent and received relative to the project base point. I’d say that currently, the best way to coordinate between Civil3D and Revit is via a Dynamo script that will transform your Civil3D elements relative to your Revit file’s survey point, so you don’t have to change how you are modelling in C3D just to get elements into Revit.