Creating amphitheatre steps

Hello guys!

I try to make an amphitheatre so I started to make a definition. However, I have a query. I divide 2 curves and i created a number of lines between them so now I want to create some steps but when i try to loft the curves I take a single surface. So I would like to know how can I create separate surfaces from lines in order to extrude them to create boxes. I tried to split the surface with the lines I have but I take an error.

Thanks in advance! (21.1 KB)

This could be one way. (20.3 KB)

Thank you very much HS_Kim!