amnesia is lagging badly can anyone help

[Warriors Curse]

my game is so laggy,quite dark and not much colour but its the lagging that has been pecking my head for days now and i just wanted to know how can i stop the lagging cause iv tried everything from loads of threads on the internet and i just cant seem to stop the lagging. iv tried changing game resolution iv updated my computer and loads of other thing so iv come to the conclusion that there is something im missing that iv not tried and i cant think what this is can you help. any help is much apreciated thank you.