Complex sentence: After all nations have entered, the president of the Organizing Committee makes a speech, followed by the IOC president who, at the end of his speech, introduces the representative of the host country who will officially declare the opening of the Games.
Split into simpler sentences: After all nations have entered, the president of the Organizing Committee makes a speech, followed by the IOC president. At the end of his speech, he introduces the representative of the host country who officially declares the opening of the Games.