The teenagers are performing tricks on their bicycles at night.
Some babies are sitting outside at night.
Teenagers and babies are two separate groups.  Sitting and performing are two separate functions.
exists e1 x1 x2 x3 x4.(n_bicycle(x3) & of(x3,x1) & n_thing(x1) & n_teenager(x1) & at(e1,x4) & n_night(x4) & on(e1,x3) & Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & n_trick(x2))
exists e1 p1 x1 x2.(at(e1,x2) & n_night(x2) & exists s1.(Theme(s1,x1) & a_outside(s1)) & Topic(e1,p1) & Actor(e1,x1) & v_sit(e1) & n_baby(x1))