Hi. From what I understand you are trying to do, the best way for the box to fall naturally, would be to add a rigid body tag to the box and a collider tag to the plane/floor. Hit play and that's it.
You can then tweak the dynamic properties, to get different bouncing, etc. for the box.
Also, I would advice you to check Nick Campbell's blog, as it is one the best C4D blogs out there (full of tutorials).
http://greyscalegorilla.com/blog/category/cinema4d/
Go trough the first set of tutorials and you'll find plenty of rigid body examples.