thanks for the reply.
the first quest you search for 4 explorers to access to a last tomb cave
I found one caged in a cave ,freed him, and another dead on a hill near the zeppelin-like aircraft in the harbor.
The last two are supposed in the map to be like this:
one dead on the first beach at the beginning of the level :I found this guy but he has nothing and being dead he can't tell me anything.The second one is supposed to be on a hill but there he is not!
By the way how can I understand which quests belong to the main story?thanks