Complex sentence: The first 99 km of the line will use the already existing Madrid-Seville high-speed railway line, from there a 67,5 km branch line will be constructed towards Alcázar de San Juan.
Split into simpler sentences: The first 99 km of the line will use the already existing Madrid-Seville high-speed railway line. From there, a 67,5 km branch line will be constructed towards Alcázar de San Juan.