A person in a hat is skateboarding and there is graffiti behind them.
The person is skateboarding.
The person skateboarding is the main point of the 1st sentence.
exists e1 p1 x1 x2 x3.(exists x4.((x3 = x4) & behind(x4,x1) & n_graffitus(x4)) & n_thing(x1) & Actor(e1,x1) & v_skateboard(e1) & in(x1,x2) & n_hat(x2) & n_person(x1))
exists e1 x1.(n_person(x1) & Actor(e1,x1) & v_skateboard(e1))