It would be better if you design the carrier system in a way that there are continuities. The building already consists of beamed flooring. Slide the two outer pillars up so that the stair outer axle is aligned with the pillars (curtain). Combine the two columns in the stairwell and turn them into a curtain. All columns are already lined up in the Y direction. No X-direction columns and curtains. So you have a curtain in the X direction. Consider Ibrahim's advice on beam sizes. You can also make the middle axle beams drooping. Increase the widths of the horizontal beams (50cm or so) Design the stairs and solve it with the system. Review slab loads at work. Do not neglect the wall loads on the floor on the floors. As Ünver said, the new regulations are valid now. However, I have made the above recommendations to improve your design knowledge. Check out the attached pictures, keep up the good work. N. YILMAZ .