Hello guys, im really really having a big problem with C4d renders
i just dont know how to use them properly.
on what position do they have to be? above the render? above all other?
and how to not lose the effect of the c4d render while using layerstyles?

There's no 'correct' way to use C4D renders.. You just have to find what fits with the sig you're trying to make.

I had major trouble at first. Now I'm starting to incorporate more and more C4Ds into my signatures developing a slightly new style. It's real fun and all it really takes is some erasing via soft brush and hard brush erasers. Make a mistake and just CTRL+ALT+Z. Easy as that. Practice and it'll get better- but of course you're going to need good c4ds in the first place.. Take a look in the c4d dump thread in Graphic Design.