Complex sentence: Elsa, not seeing her beloved, falls back to the crowd where Ortrud and Telramund take her and try to intimidate her, the Knight forces both to leave the ceremony.
Split into simpler sentences: Elsa, not seeing her beloved, falls back from the crowd. Then, Ortrud and Telramund take Elsa and then try to intimidate her, and after a short while, the Knight forces both to leave the ceremony.