A person skateboarding down a ramp at night.
A skateboarder is going fast.
A person does not have to be a skateboarder to be skateboarding.  Just because a skateboarder goes down the ramp it does not mean they are going fast.
exists e1 s1 x1 x2 x3 x4.(a_topic(x1) & at(e1,x4) & n_night(x4) & a_down(s1) & Manner(e1,s1) & Theme(e1,x3) & Actor(e1,x2) & v_skateboard(e1) & n_ramp(x3) & (x1 = x2) & n_person(x1))
exists e1 s1 x1.(a_fast(s1) & Manner(e1,s1) & Actor(e1,x1) & v_go(e1) & n_skateboarder(x1))