Ciao Federica.
Welcome on this forum!
Do you have any prior experience with Rhino and/or grasshopper?
Can you attach here your results so far?
(your second picture didn’t attach properly…)
See this Help Us Help You
If you google “grasshopper stairs” you’ll find many other examples from where to start.
I don’t know if this is your case, but generally it’s not the best approach to have everything parametrized in grasshopper.
For example, in this case the path-curve of the stair would likely be best if made manyally in rhino, a degree 5 curve, where you can manually adjust its path with the curvature graph on.
Then slicing and making steps is the funny part in grasshopper.