Complex sentence: In 1913, Porto began competing in a regional championship organised by the Porto Football Association; they won it 30 times in 34 seasons, 20 of which consecutively between 1918 and 1939.
Split into simpler sentences: In 1913, Porto began competing in a regional championship organised by the Porto Football Association. They won it 30 times in 34 seasons, 20 of which consecutively between 1918 and 1939.