Complex sentence: Karl Renner, the first Chancellor of post-WW1 Austria, was appointed as Austria's first Chancellor, this appointment lasted until the end of 1945, when Renner became the first President of the Second Republic.
Split into simpler sentences: Karl Renner, the first Chancellor of post-WW1 Austria, appointed as Austria's first Chancellor. This appointment lasted until the end of 1945, when Renner became the first President of the Second Republic.