Some items doesn't want to render + extra problem: material

I made a 3D logo from a 2D one and i’m happy with I made so far, but when I push the render button then not all Items are getting rendered. Weird is after a few times clicking then they render still. In my example I mean the (wheels). Is this a bug?

Second problem is the material. I did download a liberary with materials, but stil I’m not able to get a real metal one. The D and surroundings of the wheels where suposed to be metal.

search my name and you should find somthing titiled “EASY METAL!!!”
that might help you.
but i think thata big part of your problem is that you dont have anything for your metal to reflect. i’m not sure, but hdri might be what youre looking for.(i’m still trying to figure out how to use them though, so i may be wrong.)