Ok so i could not play G3 these days(school..) and thanks for your answers, i'll see tomorrow when i'll have some time to play .
About Lago, i remember i tried to kill Fabio but as i said, the liberation start when i attack him. It seems there is no way to lure him out of village or anything else without the guards to know ( even if they don't see the fight ). If there's no other way to get that key, i'll liberate the.. village.