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also I want to play two but I heard about how hard it is so I want to know what one I should be starting with if two is as hard as I have heard.

My experience with 2-3 is limited but I've beaten 1 several times and 4 once (not that 4 counts).

I would highly recommend starting with 1, it's the simplest and probably the easiest to learn (3 seems to add a bunch of features). G2 Night of the Raven seems to be rather difficult.

I'm replaying G1 already and I really enjoy it.

For story reasons you'd want to start with the first Gothic (some characters reappear in the sequels, and past events are mentioned from time to time) but this knowledge isn't required for playing the game properly.

Gothic II's increased difficulty is due to installing the Night of the Raven expansion by default but you can deselect this in the installer's options to get the original Gothic II experience.