Complex sentence: Ismay and the board of the White Star plan to manipulate the stock by selling even their own stock in order to buy it back at a lower price just before the news about the record speed of the ship is published to the press.
Split into simpler sentences: Ismay and the board of the White Star plan to lower the stocks by selling even their own stocks in order to buy them back at a lower price. They plan to buy them back just before the news about the record speed of the ship will be published to the press.