The man with the full face mask is riding down a grassy hill
A man is riding outside.
Man with the full face mask is a type of man, and grassy hill implies outside.
exists e1 s1 s2 x1 x2 x3 x4 x5.(n_mask(x2) & of(x2,x3) & n_face(x3) & a_full(s1) & Theme(s1,x2) & n_man(x1) & a_down(s2) & Manner(e1,s2) & Theme(e1,x4) & Actor(e1,x1) & v_ride(e1) & n_hill(x4) & of(x4,x5) & n_grassy(x5) & with(x1,x2))
exists e1 s1 x1.(a_outside(s1) & Manner(e1,s1) & Actor(e1,x1) & v_ride(e1) & n_man(x1))