Thank you all for your answers, but I would like to ask whose fault is in this situation:
For example if I land the kite on the beach and somebody(another kite surfer without kite) took the kite, and put it on the ground in landing position. I unhook and at the same moment kite starts rising and injure someone.
These situations are pretty similar and if we would go to judge I don't think that he would say your gear - your fault.
Always the kiters fault. Not the owners, but the person flying the kite.
First the kiter has to choose the lander, and also should be prepared to self land if a contingency occurs.
If somebody catches the kite: The kiter should wait until they know the kite is secure to stop flying it, then to unhook and run to the kite. Not stop, wrap the lines, have a smoke and take a leak before going to the kite. Even if the lander slips and accidentally lets the kite loose while holding it its still the kiters fault so take responsibility and go to the kite quickly and secure your kite.
When I catch a kite, I hold it upside down and give it to the owner to secure it on the beach so if it blows away there is no question.
If a friend is catching your kite while you are both flying kites and one crashes, that is just bad luck.
Finally, If you are talking about going to court for kitesurfing: that really takes the fun out of it and you certainly aren't friends.