Namespce Error!!!!!!!!!

'The type of namespace name 'EventSystems' does not exist in the namespace 'UnityEngine' (Are you missing an assembly reference?)'

This comes up with my script and I am unsure of how to fix it. Can someone please help

Also a lot of my scripts have errors that i cannot fix (being a nube) is there any program i can get to debug my game. I have Mono develop (I have windows) but i dont know how to properly use it

(I cant put a picture of the final bit of thee script so here:}

     public void OnPointerUp(PointerEventData data)
     {
         m_Axis.Update(Mathf.MoveTowards(m_Axis.GetValue, 0, responseSpeed * Time.deltaTime));
     }
 }

})

PLEASE HELP