How can we win at Bohnanza: Al Cabohne?
For the most part, you can use any Bohnanza guide to win at Al Cabohne. All you have to take into consideration are the fundamental differences between this game and regular Bohnanza. I'll focus on those:

The most important difference created with Al Cabohne is in the way the discard pile affects the proceedings of the game. You can get some good value out of the discard pile if you can manage to remember which cards are on there.

Also something to look out for, if one of the mafia bosses ends up with a bean that you already have, you might not want to harvest them immediately. If your harvest goes onto the discard pile, that's basically the same as giving it to the mafia. If you think you can manage until the mafia harvests their field you can try to get all those cards from the discard pile back onto your field. So unless you really need the space, try to keep these beans on the table.