Complex sentence: First it became a permanent building, whose roof could sometimes be used to make speeches and then as time passed it was raised up from the level of the orchestra, creating a proskenion, or "space in front of the" skene "".
Split into simpler sentences: First it became a permanent building, whose roof could sometimes be used to make speeches. Then it was raised up from the level of the orchestra, creating a proskenion, or "space in front of the" skene "".