Complex sentence: Before the self-propelled barges, the barges were hauled with two to four horses or mules til the beginning of the 20th century, then came the tractors, first on railways then on tyres since 1933, with electrical motors first and later diesel engines.
Split into simpler sentences: Before the self-propelled barges, the barges were hauled with two to four horses or mules, til the beginning of the 20th century. Then came the tractors, first on railways then on tyres since 1933, with electrical motors first and later diesel engines.