Complex sentence: She currently competes with her 16 year old chesnut gelding Elton (Ehrentusch/Philipo), prior to Elton she successful rode a mare, "Die oder Keine" (Donnerhall/Rubinstein) before she retired from competitive events.
Split into simpler sentences: She currently competes with her 16 year old chesnut gelding Elton (Ehrentusch/Philipo). Kalan previous rode Die oder Keine (Donnerhall/Rubinstein) before the horse retired from competitive events.