Two bishops beat a knight, but only by separating the knight from its king, driving the king to the edge, and dominating the knight so that it has no safe squares. The win can take over fifty moves from the worst positions; know the method and watch the move count.
Two bishops against a knight is a theoretical win, but it is one of the longest elementary endings; some positions need more than fifty moves even with best play, and this is a shorter checkpoint (mate in about twenty).