Complex sentence: The culmination of his life's work was a printing of the Bible in Belarusian though it is difficult to determine precisely what language he used as there was no conventional Belarusian language as we know it today.
Split into simpler sentences: The culmination of his life's work was a printing of the Bible in Belarusian. It is difficult to determine precisely what language he used as there was no conventional Belarusian language as we know it today.