Objects don't know up in Game Engine.

So I tried playing my blender project in game engine, but some of the objects don’t show up at all. The ones that do show up don’t have any material to it. Can someone help me? I’ve put a link to the file.

First: Material looks like cycles node (diffuce bsdf) material, that dont work with ge, it is for cycles renrerer.
Second: You have restrict object view from render (camera symbol in the outliner). That makes object to invisible in ge.
Nice tank by the way, just make textures and physics and rock and roll.