Complex sentence: Algirdas not only succeeded in holding his own, he also acquired influence and territory at the expense of Muscovy and the Golden Horde, and extended the borders of the Grand Duchy of Lithuania to the northern shore of the Black Sea.
Split into simpler sentences: Algirdas not only succeeded in holding his own, he also acquired influence and territory at the expense of Muscovy and the Golden Horde. In addition, Algirdas extended the borders of the Grand Duchy of Lithuania to the northern shore of the Black Sea.