But how does it work with the graphics... if anybody goes 2 steps right. Must the screen complete repaint?
Some older games (a long, long time ago, in a galaxy far, far away...) used what's called "Dirty Rectangle" painting, which amounts to redrawing only the areas that have changed. This worked okay for large areas where only a little bit changed. However, when you add in scrolling, special effects, cool text popups, etc., it just gets easier to repaint the entire screen. Modern hardware has more than enough horseypower to do it, so don't fret full screen repaints.
And does they use a database or how could the player communicate?
How do you mean? They probably have a database to keep track of players, stats, and other persistent information, but actual communication is probably done in a client/server fashion.
I programmed browsergames, but that was easy. I just read the database or update the database. Functioned that similarly?
Sort of. The difference is that you really need to develop your own client server protocol (or purchase a $$$ package to do it for you).
Sorry for the bad english, i come from germany...
It's okay. As long as you take the time to do the translation as best as you can, we'll happily work with you. :-)