Whatever, new question:
I want to make it possible to run in houses, following this: http://www.pokecommunity.com/showthread.php?t=207026
BUT I don't know how to do this, can anybody pls help me?
As for the running inside buildings, I had seen that thread long ago but discovered a MUCH easier way of doing it. It won't be the same since you have the German FireRed though but if you use an English version you would go to the offset 0xBD494 in a HEX Editor and change the value from 08 to 00.