With the help of @sovitek, I managed to break the Revit 2022 triangulated geometry (link) into surfaces and categorize these in terms of their orientation as suggested in this post: link
This is the picture of the Dynamo script for doing that (and link to the file itself: link):
Now, the problem is that I want to identify, which of the surfaces in each orientation are co-planar and intersecting to apply Surface.ByUnion node. I have thought of approaching this issue through identifying identical vertices and/or edges but this requires implementing loops, for which I do not yet have competencies to implement in Dynamo.
@sovitek, basically, this works, but due to the problems in the dataset, there is an anomaly. Namely, the buildings, which do not have the Building Registry Code in the Estonian Digital Twin System are exported as one object. See the picture below from Revit:
No matter which one of all these blue buildings I choose in Revit, all will be selected as one. That is why I thought that checking the co-planrity would be the approach to use!?