Complex sentence: In August, she achieved her lifetime best of 1:59.67 at the Berlin grand prix, then at the European Championships in Stuttgart, she reached the semi-finals and ran 2:02.03.
Split into simpler sentences: In August, she achieved her lifetime best of 1:59.67 at the Berlin grand prix. Two weeks later at the European Championships in Stuttgart, she reached the semi-finals and ran 2:02.03.