A boy wearing green shorts is about to serve a volleyball.
A boy is about to mess up his serve.
About to serve a vollyball can mean the boy might make his serve or that he is about to mess up his serve.  There is not enough information.
exists e1 p1 s1 s2 x1 x2 x3.(Topic(s2,p1) & Actor(s2,x1) & a_about(s2) & exists e2 x4.(Theme(e2,x4) & Actor(e2,x1) & v_serve(e2) & n_volleyball(x4)) & Theme(e1,x3) & Actor(e1,x2) & v_wear(e1) & n_shorts(x3) & a_green(s1) & Theme(s1,x3) & (x1 = x2) & n_boy(x1))
exists e1 p1 s1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_serve(e1) & n_thing(x3) & a_about(s1) & Manner(p1,s1) & exists x4 x5.(to(x2,x4) & up(x4,x5) & n_his(x5) & n_mess(x4)) & (x1 = x2) & n_boy(x1))