here are your answers
1/ Black flower : can one use a club card as a bang even though he doesn't have a bang in his hand ? Yes
2/ Tuco Franziskaner : if he is the sheriff does he have 6 life points ? Yes, as sheriff he has 6 life points. In case he has a dynamite in front of him, his effect doesn't trigger.
And what happened to his ability if he has a dynamite in front of him ?
3/ Does a ghost can keep the blue card in front of him at the end of his turn ? Yes. He must discard his hand of cards since he has 0 life points - so he cannot keep cards in hand at the end of his turn. However, this limit is not applied to the cards in play.
4/ Fanning : what happen if the player next to the first player has a mustang ? He is not affected by the Fanning.
And then few questions about the regular bang :
5/ Is it possible to put a weapon (blue card) in front of another player ?
No, it is not possible unless specified on the card (see Ghost from Valley of Shadow or Jail from the regular BANG!)
6/ Is it possible to use panic on himself (especially on the card in front of us) ? Yes, you can. Same with playing Cat Balou on yourself.
No, you cannot play a card if you already have another one with the same name in front of you.
7/ If A player already has a volcanic card in front of him, can he paly another volcanic card and discard the one in front of him ?[/
Hope this helps