Codeigniter 3 Url without controller

Hi,

I'm struggling to get my project even started.
I'm trying to remove my controller name from the url witch was easy on Codeigniter 2.0.
But now i don't get it working. Can someone please help me out so I can update my old website again.
I hope i don't have to add every single page in the route because it wil get to full.

I must say if I load a page like this:
www.example.com/function

The page loads correctly the function of the default controller
but when i add parrameters like
www.example.com/function/id

The page won't load and tries to load the Function as Controller

Can someone please help me out i'm really stuck on this.