I have a 6 lights controlled by 2 normal switches (2 Way Circuit). I want to replace one of the normal switches with a dimmer switch.
Is this possible?
Yes, you just have to buy the right dimmer. Here in the USA, most dimmers are compatible with 3-way circuits. I'm not sure if that's true in your area, so you'll have to verify when buying the dimmer.
NOTE: In the USA we would call this type of circuit a 3-way, while other countries (yours included) refer to it as a 2-way circuit.