Corrections

Deletions

Self-Discovery

The summer makes has the effect of reconnecting to the person with his or her own body, maybe due the fact of wear that he or she wears less clothing. the The body ceases to be a bunch of pieces to be and is just one piece, and also the skin becomes vulnerable to each stimulus sensation.
She was thinking about this when suddenly she starts started to staring stare at her hands, stretching every finger, linking it them and touching her hands with to her mouth to raises raise the perception sensation, and then she starts started to touch her arms, her legs, squeezing, caressing and scratching them, softly in the beginning and then strongly.
She slips slipped her finger through along each one of her veins, feeling the warm warmth of every pulsation and feeling how the blood gathers gathered in certain areas of her body. Then she focuses focused in on her heartbeat, that music that is always with us but we aren't aware of it.
After a few minute minutes of this game of self-discovery, she feels felt that her body sinks sink little by little, and is it was in that moment when her unconscious begins began to work, jumping from one story to another, as if leafing through a book.
Finally, he it choose one story. One story that he it enjoys and also she enjoys.
And that is when she start started to dream.

The summer makes the effect of reconnect to the person with his[their] own body, maybe due the fact of wearing less clothing, the body ceases to be a bunch collection of pieces to and becomes just one piece and also the skin becomes vulnerable to each stimulus.
She was thinking about this when suddenly she starts to staring at her hands, stretching every finger, linking it and touching her hands with her mouth to raises increase the perception sensation, and then she starts to touch her arms, her legs, squeezing, caressing and scratching them, softly in the beginning and then harder strongly.
She slips her finger through over each one of her veins, feeling the warmth of every pulsation and feeling how the blood gathers in certain areas of her body. Then she focuses on her heartbeat, that music that is always with us but we aren't aware of it.
After a few minute of this game of self-discovery, she feels that her body sinks little by little, and is in that moment when her unconscious begins to work, jumping from one story to another, as leafing through a book.
Finally, it choose one story. One story that it enjoys and also she enjoys.
And that is when she start to dream.

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I don't know who 'he' refers to, Bárbara. You haven't 'introduced' a secong person.

You have put "his own body" but it's ok to use "their own body", even in the singular, because it's gender unspecific.

'strongly' isn't the right word for "squeezing, caressing or scratching"

For example: "squeezing harder"