Complex sentence: Meanwhile, Marko has found a way to enter the building through an underground sewer passage and posing as a doctor manages to enter the hospital room where Franz, Natalija and Bata are talking.
Split into simpler sentences: Meanwhile, Marko has found a way to enter the building through an underground sewer passage. Posing as a doctor, he enters the hospital room where Franz, Natalija and Bata are talking.