Question

why it is difficult to go on ramp rather than climbing stairs

Answer 1

on steps the surface is horizontal perfect hence the gravitational pull is equal on all sides on ramp however the surface being slopy the gravitational pull is more of the other side.Hence it is difficult to go on a ramp than climbing stairs.

Answer 2

You have to lift up your body mass under the presence of gravity, so you have to overcome the force of gravity. While climbing up the stairs you have to put force on ground, more then your weight, which put same force but in opposite direction i.e. on you