Now I realize what my questions was. So here it is: What change the laws about the steadly reincarnation for the mayhanapractioner and the theravadapractioner that doesnt beeing reborn? Is it enought to take some wows?
You are asking why the Bodhisattvas can be reborn over and over again?
This is one of the questions stated in the Abhidharmasamuccaya and it answers as follows ->Why does a bodhisatva who has entered into the commitment of a bodhisattva not become a stream-enterer?
Because the stream is imperfect with regard to practice of the Path.
Having attained the Truths by clear understanding, the bodhisattva cultivates the path counteracting the obstacles to the knowables by means of the ten-stage Path of cultivation; but he does not cultivate the path counteracting the obstacles of the defilements.
Usually Mahayana practicioners will also tell you that you have to resolve to Bodhicitta (which is a kind of vow) and that this Bodhicitta somehow will become a part of your mindstream. I have not read any text detailing / explaining this tho as far as I can remember nor can I tell you when this concept was first introduced in the history of Buddhist thought.