Complex sentence: He worked as a child fisherman in more than 20 villages along Lake Volta from the age of 6 to 13, before he finally liberated himself at the time he could neither read nor write.
Split into simpler sentences: He worked as a child fisherman in more than 20 villages along Lake Volta from the age of 6 to 13, before he finally liberated himself. At the time he could neither read nor write.