Complex sentence: Each block of phase 1 (or 3) has 3 major steps when you look from sides, there are 5 floors in first step, 9 in second and 12 in the third one.
Split into simpler sentences: Each block of phase 1 (or 3) has 3 major steps. When you look from sides, there are 5 floors in first step, 9 in second and 12 in the third one.