The young man is surfing.
The young man doesn't know how to surf.
Surfing does not imply doesn't know how to surf.
exists e1 s1 x1.(n_man(x1) & a_young(s1) & Theme(s1,x1) & Actor(e1,x1) & v_surf(e1))
exists s1 x1.(n_man(x1) & a_young(s1) & Theme(s1,x1) & -exists e1 x2.(Topic(e1,x2) & Actor(e1,x1) & v_know(e1) & n_manner(x2) & exists e2 x3.(Actor(e2,x3) & v_surf(e2))))