A boy speeding down a steep slide.
A boy swinging in the air
Speeding down a slide can't be done while in the air, because being in the air would mean you aren't touching the slide. Also swinging can't be done while sliding down a slide, they're two different objects.
exists e1 s1 s2 x1 x2 x3.(a_topic(x1) & a_down(s2) & Manner(e1,s2) & Theme(e1,x3) & Actor(e1,x2) & v_speed(e1) & n_slide(x3) & a_steep(s1) & Theme(s1,x3) & (x1 = x2) & n_boy(x1))
exists e1 x1 x2 x3.(n_air(x3) & a_topic(x1) & in(e1,x3) & Actor(e1,x2) & v_swing(e1) & (x1 = x2) & n_boy(x1))