Complex sentence: Two of the former six through tracks were removed, along with the platforms 12-17, two new platforms were built, Covered by the Arena, which was joined to the station by means of a raft above the station's through platforms.
Split into simpler sentences: Two of the former six through tracks were removed, along with the platforms 12-17. The Arena was joined to the station by means of a raft above the station's through platforms.