I created a model in 3ds max and exported it as .3ds but when I import it in keyshot, it does not import the original materials. Is there a way to import 3ds max models (.3ds files) without losing their textures?
You can't use Max Materials/Shaders in Keyshot directly you'll have to use Keyshot's own materials. You can use the same textures but you will have to reapply them.
When you have applied a material to a part in keyshot right click on the part to open the material editor, you'll see two map buttons, one for textures and one for bump/normal maps use these to reapply the textures.
If the textures are in the same folder as the geometry file, they will automatically be applied. The default material is "advanced". You can simply change the material then by double clicking on the material. In the material editor, simply change the material itself. The textures will be retained.