An impromptu toast among friends.
Friends have gathered together.
Have gathered together is rephrasing with more info of toast among friends.
exists s1 x1 x2.(a_topic(x1) & among(x1,x2) & n_friend(x2) & n_toast(x1) & a_impromptu(s1) & Theme(s1,x1))
exists e1 p1 x1.(exists s1.(Theme(s1,x1) & a_together(s1)) & Topic(e1,p1) & Actor(e1,x1) & v_gather(e1) & n_friend(x1))