Complex sentence: The railway lines were put on elevated embankments and the trackbed inside the station was raised, the old station building, originally built as an island platform, was torn down and superseded by the current building, the construction of which was finished by 1920.
Split into simpler sentences: The railway lines were put on elevated embankments and the trackbed inside the station was raised. The old station building, which was built as an island platform, was torn down and superseded by the current building, the construction of which was finished by 1920.