Place a 3D building instead of real building my question is, how can I put 3D elements into a real footage. For example an 3D Building instead of a existing Building, so that I can destroy the 3D building for example? So that the 3D Building looks real in the footage.

I hope you understand what I mean
You can use Camera Tracking to do that, here is a YouTube tutorial (Blender Guru)

That explains how to do it in detail:
https://www.youtube.com/watch?v=CVPcT0dJmoY