What do you want to know?I want to know about my girlfriend's safe days when & who it happens.
There are really no safe days for sex. Women ovulate at different times. Some women ovulate right before their periods.
During the average 28 day cycle a woman will ovulate around day 14 of her cycle, at most there is a viable egg for 48 hours, and around a week leading up to ovulation there is fertile cervical mucus which is what allows the sperm to enter the cervix and allows it to remain in the vagina for up to a week. So during the average menstrual cycle a woman will be fertile around days 7-16, and all other days of her cycle she is infertile so can have sex without risk of pregnancy.
Everyone's menstrual cycles are different and cycles can change, thus the only way to know when you are fertile or not is to use Fertility Awareness Method - this is where you track basal body temperature, cervical position, cervical mucus, and secondary fertility signs on a daily basis to determine exactly when you are fertile or not on a day-by-day basis. Fertility Awareness Method when used correctly is 98% effective against unwanted pregnancy.
If you are not using Fertility Awareness Method then you have no way of knowing when you are fertile or not, thus you must assume you could always be fertile - if you don't want to fall pregnant then you'd have to use another birth control method other than Fertility Awareness Method.