I am new to Blender so I started to watch tutorials. Recently i have been doing tunnel tutorial. But i have problem with rendering.

As you can see on the picture above there is a problem with tracks and walls. As for the walls i dont know if it is a issue with textures or rendering. But on the rails there is no textures, yet there is a problem. I tried to render only rails and lights and i still get same result. I am rendering on Blender render. I am working on default Blender settings, so maybe i need to adjust settings to my computer. Best regards