It's it safe too douch with baking soda and why?

No need to douche. The vagina is an amazing organ- it keeps itself clean without the help of any soaps or douches. There are "good" bacteria in the vagina that help keep out the "bad" bacteria, and douching too much can lead to a change in the bacterial flora of the vagina. This can predispose to infections such as bacterial vaginosis. You can clean with water and gentle soap around the outside of the vagina.