I am a bit of a newbie with cinema 4d but I have worked with 3ds max and sketchup for a while now. ok so I drew this model on sketchup and then imported it on cinema 4d as an obj file, everything was fine BUT anything that had a hole extruded out, they came out weird, so I deleted those, redrew a polygon by joining the vertexes, subdivided the polygons and extruded the portion of the polygon that I wanted. Now, for some strange reason, when I extrude and render, the scene appears as if I applied something like turbosmooth on it! why is that? here are some screen shots
That looks very much like you have a Phong Tag applied to the object that either has the 'Angle Limit' checkbox disabled or the 'Phong Angle' set too high.
The Phong Tag smooths face normals across edges. It has a threshold 'Phong Angle' value that allows you to define at what point two face normals have diverged enough to NOT smooth across the edge. In general a value of somewhere between 60 and 80 degrees tends to work well. That's where I'd recommend starting.
You can also manually break the phong shading on selected edges using the Mesh > Normals > Break Phong Shading command but that's a corner case.
just in case you're still having this issue,
I've been searching around workflows between Sketchup and C4D.
As Darby mentioned it, make first sure that Phong tags are applied when importing from Sketchup.
The other trick is that surfaces are not buil the same way in sketchup and C4D, so select all your object's points at the point-edit mode level (French version, so I'm not really sure about its english name, left-bar icon), and on the right-click menu, choose optimise, it should merge close points at the value you select, in this case 0.00, so that overlapping points merge. Previously to this operation, all faces are locked apart from the others, so phong smoothing operations arenot physically applicable. After this, your object is one, and faces do edge properly.
Hope it may help,