Complex sentence: At the same time he also engaged in exploring and struck up a close friendship with the Governor of Harar, "Ras" Makonnen Wolde Mikael, father of future emperor Haile Selassie.
Split into simpler sentences: At the same time he also engaged in exploring. During this period he also struck up a close friendship with the Governor of Harar, "Ras" Makonnen Wolde Mikael, father of future emperor Haile Selassie.