Does a man nullify his first circuit (of Tawaf) that he performed due to intense crowding when he moves to the roof, or does he build upon it?

There is no harm in building upon the first circuit of the Sa'i and completing it on the upper floor, if the one performing Sa'i began their Sa'i and then found the crowd difficult, so they moved upstairs. This is because the entire Mas'a (place of Sa'i) is considered one, and there is no long duration between the transitions.