I looked in a couple of documenations and tried to search the forum (but it is temporarily not possible) and couldn't find what I was looking.
Alright, is there a !bang that increases and/or decreases the System volume?
And also, does anyone know to how assign functions to notebook or keyboard specific buttons?

The link den an appropriate documentation would be enough I guess, but explanations are always welcome. ;7

yes - Search for volume on Loose-Screws
yes - Read our jKey documenation

Thank you very much.

v_bang (or lsslider if you're already using it) can do volume and to set your keyboard keys for volume controls, use skankey and jkey together.