Complex sentence: Dren Mandić, from the Serbian team, decided to attend to his oxygen system and so unclipped from the rope, to let other climbers pass; he lost his balance and fell, bumping into Cecilie Skog of the Norwegian team.
Split into simpler sentences: Dren Mandić, from the Serbian team, decided to attend to his oxygen system and so unclipped from the rope to let other climbers pass. Mandić lost his balance and fell, bumping into Cecilie Skog of the Norwegian team.