I mean for example how much minutes I need to do breathing exrisce before trying to be able to enter to a trance stete?
Its individual and takes practice, to get feel for it.
See for yourself by trying and practicing, start from less, and gradually you can add up one or two reps time by time, when you feel relaxed and still, you can trance, but when you are still relaxed and meditative by continuing meditation naturally will bring you into light trance, and you can go deeper,
Blue light meditation is very helpful, blue helps enter trance, and relaxes, it is very nice.
Breathing exercises where breath is hold are best to still mind and relax, alternate nostril, basic yogic breath and etc.
Instructions from how much reps you can start if you are beginner is in JoS.
Normally to enter light trance, 10 reps of basic yogic breath is enough if done right.