@Marta-Alicia0 Yes, I know that we definitely have a tourist season in Mexico and probably where you are as well? So good booking rate about half the year, and then super slow down. So if most of your past guests have been tourists, that could explain poor booking rate. But maybe you get people also in the city for business or other reasons?
I can't comment on your pricing, as I don't know what other listing go for in your area. $20 for 2 people seems really inexpensive. The best way to figure out pricing is to go onto the airbnb site as if you were a guest (log out of your account first and then just go on the site as if you were someone without an airbnb account) type in San Salvador, and type in the filters a guest would use for your place- 2 guests, one bedroom, private bath, etc. Then compare your pricing with other listings that come up. And keep in mind that just because a listing is set up for the same number of people as yours, with similar amenities, doesn't mean your price should be the same- just because a place sleeps 2, with private bath, use of kitchen, etc doesn't mean it is comparable- it may be a dumpy, ugly place as compared to yours, they may have reviews saying it was dirty or that things were not as advertised. Look at the photos and reviews, in addition to the prices for other places in San Salvador.
And don't price yourself too low- that tends to bring some poor quality guests and you don't want to be cleaning and providing amenities and paying for utilities for almost no profit. You have to strike a balance between what people are willing to pay in your area with what makes it worth your while to host. I could probably up my price a bit, as this is a very expensive town, but I like to keep it affordable and I determined that I can list for the price I do and still not feel like I'm hosting for peanuts.