I am just learning how to use 3D rendering programs, that's because I am still young, and I need some help with Bryce. I can't figure out how to export anything but mountains and things from Bryce. I want to export some of my walls and buildings I have made to .3ds How can I do that?

No can do. Bryce will only export terrains.Sorry.

you can export nearly everything from bryce.select the objekt, click to the "e" which is beside the objekt,than hit ctrl+d

This is not correct. The Edit Mesh/Ctrl+D trick ONLY works for objects which are Imported Meshes. Spheres, cubes, cones, pyramids, etc. don't have an Edit Mesh dialogue box, so they can't be exported this way. Any object or group can be exported as a .obp file, which is a proprietary Bryce format usable only within Bryce as an object preset. So it's no good to export to other programs. The only objects which can be exported from Bryce to other programs are mountains/terrains (you figured that one out already), and Imported Meshes (created externally anyway), using the Edit Mesh/Ctrl-D trick. All other objects can NOT be exported. Bryce is a renderer and a texturer. It is not designed to be a general-purpose modeller. For that, grab another program, such as Rhino, Ray Dream, Carrara, TrueSpace, etc.