Complex sentence: That morning, Sokolowski neared the border by Clara-Zetkin-Straße (now Dorotheenstraße) close the Brandenburg Gate and the Reichstag building when an East German border guard saw him and fired a warning shot, but he failed to respond.
Split into simpler sentences: That morning, he neared the border by Clara-Zetkin-Straße, which is known today as Dorotheenstraße. A border guard saw him and fired a warning shot, but Sokolowski failed to respond.