My menstruation is start 1 dec and i don't want to pregnant, so how many days stopped sex with my partner"?

Depends: It depends on the length of your cycles. If your cycles are 28 days long, then you will probably be most fertile between 11 and 16 days after your period started. If your cycles are longer or shorter this will change the fertile time. Visiting a website on natural family planning can give you more information on predicting your fertile time.

Contraceptives best: Birth control pill for you or condom use by your partner is much more reliable that the so called "safe period". You can have sex at any time during your menstrual cycle if you use one of these. There are also long-acting contraceptive implants. Suggest you discuss with your gyn dr.

As many as desired: A woman can remain "stopped sex" for as many days as she wishes, and she should not get pregnant. She can take that time to decide on a good form of birth control, which may require her seeing a doctor. Condoms are very effective and don't require seeing a doctor. As soon as she has "started sex" again, she may get pregnant if not using birth control of some type.