After a change of graphic card to Nvidia I decided to install the nvidia driver...hrm, of course the installation give me an error x( The error says that I have wrong kernel interface. What is that?! It tried to connect and download the right kernel interface for me but I don't have a internet connection >_<; Where to download? Then one more error came up, it said that it couldn't build my kernel module. What to do? Well, there was some questions that I really want to have an answer to.

Install kernel headers, kernel source, a compiler (gcc) and "make" using your distro's package manager and let the installer build a module for you.
If you get the driver installed and later change/update your kernel you will need to rerun the driver's installer.

The NVIDIA drivers have a very good README file too.