Right Speech & Precepts Couple of questions:


According to the Dhamma, is it allowed to critisize someone in a constructive manner?
If someone gossips about me how do I deal with it? Compassion and kindness aside, sometimes it is necessary to be assertive. One can only be compassionate if one is healthy inside in that moment in time.
Intention is a little bit more important than the act itself,
(isnt it- at least in Buddhism) (only in a few instances is the act more important than the intention for example stealing is wrong even if one's family is poor), however, if for example I slice my bread in the supermarket and I see remaining pieces of bread in the machine and I take them with me because no one did I then so no reason why I would largely violete the "not taking what is not given". Sure, it wasn't given but if my attention or thought is: "Well, if I don't take it it will be wasted" then that should rather influence my kamma, right? So it's largely about my intention. If I  hurt someone out of compassion because he attacks someone and injures them severely I have better results because my intention was to safe others, correct?
You can criticize if it is beneficial to you and/or others, but you should not get angry.
You can advice the person not to do so, if you think he will listen. In any case, be mindful of the concern about your ego. You cannot really stop people from talking whatever they like behind your back. Be mindful of the anger arising in you. Do either Metta or Satipattana meditation to deal with anger.
Intention takes precedence always. It's never the act. Stealing is wrong because it is caused by greed and delusion. Regarding sliced bread, taking something is ok if the owner does not mind you taking it. It does not break the precept. You can prevent someone from hurting another by blocking his path or holding him tight. But hurting intentionally usually involves aversion. It's up to you to check if hate/aversion creeps in.