A short story

Once upon a time there was a little girl who was lost in a the center of the Barcelona. She looks was looking for her home. She was living lived in a small, old flat in on the fifth floor of a building without with no elevator, [see note below] with poorly painted walls and broken furniture.

When As she walked indown the street, she met meets a small rat that was playing a Spanish guitar on the corner. and She asked it if he knows knew the Cervantes Street, but the rat didn’t know this that street. The rat tells told her that if she wanted to find this that street she had to sing his song called “¿Ole ole? ¡Ole!” The little girl kept walking and singing the “¿Ole ole? ¡Ole!” song.

She didn’t stop walking when she found a bifurcation [bifurcation is a scientific term in English, most people don't know this word] came to a crossroads. She asked themselves wondered which was the right way to return get to her house…

Since you write "flat" I assume you're writing for a British/European adience, as American English would say "apartment", and they would call it a "fifth-floor walk-up" to indicate that she's on the 5th floor with no stairs. But I'm not certain "fifth-floor walk-up" is correct for British English.

A Short Story

Once upon a time there was a little girl who was lost in a the center of the Barcelona [better would be, "the downtown of Barcelona". She looked for her home, . She was living in a small old dilapidated flat on fifth floor without no elevator, paint crumbling from the walls . with poorly painted walls and [of course,] broke furniture with pieces missing here and there. [Just to show you how to express the same thing in other ways]

When As she walked in the street, she saw meets a small rat that playing a Spanish guitar on the corner. She paused [to give some dramatic flair] and she asked it if he knows the where Cervantes Street was.  but The rat didn’t did not know the address but told  this street. The rat tells her that if she wants to find where she wanted to go, all she had to do was this Street she has to sing his song, called “¿Ole ole? ¡Ole!”

The little girl followed the rat's advice and continued kept walking and singing “¿Ole ole? ¡Ole!”  at the same time.song.

She didn’t did not stop walking when until she found a crossroad/junction/intersection bifurcation [or "the road that started to bifurcate".  Still this is a big word that is rarely used in such a simple context.]. The she asked themselves herself which was the right way to return her house…

Good short story with a cliffhanger.

what a good writer you are becoming! This story has a small problem with tense. It happens in the past, but you are writing in the present. They must be the same. I will put it consistently into the present tense although stories are generally told in the past tense--thus the 'once upon a time.' You should try it again in the past tense.

A short story

Once upon a time there was a little girl who was is lost in a center of the Barcelona. She looks for her home. She was living in a small, old flat in fifth floor without elevator, with poorly painted walls and broke furniture.

When As she walks in the street, she meets a small rat that play is playing a Spanish guitar on the corner, and she asked asks it if heit  [pronoun must be consistent; it's either an 'it' or a 'he'] knows the where Cervantes Street is, but the rat didn’t know this streetdoesn't know. The rat tells her that if she wants to find this Street, she has to sing his song called “¿Ole ole? ¡Ole!” The little girl kept walking and continues to walk while singing “¿Ole ole? ¡Ole!” song.

She didn’t stop walking when she found a bifurcation. She asked themselves which was the right way to return her house… She comes to an intersection and asks herself which way she should turn to return to her house.