Here is an edited version of your first chapter I tried to focus on just correcting the obvious typos without changing or adding to much of my own words. I know writing in a second language can be tough as I have helped friends previously when they started translating their work into English. I would recommend having a friend who knows English proofread your work or running your writing through a spell checker before publishing it.(Granted the chapter I edited here is over two years old so I don't know if you have gotten any better.)
[You are a boy, 18 years old. Your name is Tim and you have a wonderfull girlfriend, enveryone arround you are jalous about her. She is the perfect girl, angel face, slim with perky and perfect breast and ass] changed to --> You are a boy, 18 years old. Your name is Tim and you have a wonderful girlfriend, everyone is jealous of you. She is the perfect girl, angel face, slim with perky and perfect breast and ass.
[But a morning she is standing at your door and she's not the same anymore...] changed to --> However this morning she is standing at your door and she seems foreign to you. (Side note does Tracy not live with the boyfriend? if so it's a little strange for the first action they have after possessing Tracy would be to run to his door.)
[She is acting weird, and looking at herself in the mirror like she has never seen her perfect face and body.] changed to --> She is acting weird, and looking at herself in the mirror like she has never seen her perfect face and body before.
["Oooh yes! And I think I've never been this good for a very long time! " Tracy said with an evil smile] changed to --> "Huh, I'm fine! I haven't felt this good in a long time! " Tracy said with an evil smile.
[With that she look at you with hungry eyes, removing her top and approaching you. She then kiss you like a godess, taking your cock in her hand.] changed to --> With that she looks at you with hungry eyes, slowly removing her top as she approaches you. she then begins kissing you like a goddess, taking your cock in her hand.
[You: "I don't know, it was different... You are a bit strange, are you sure you are feeling good?"] changed to ---> You: "I don't know, it was different... You are acting a bit strange, are you sure you are feeling ok?"
[Tracy: " Look at me little boy, with a body like that who would'nt feel good??!! Aha"] changed to ---> Tracy: " Look at me little boy, with a body like this who wouldn't feel good??!! Aha"
[You: "Tracy you are forgeting your top!"] changed to ---> You: "Tracy, you are forgetting your top!"
[She put her top back on and said: "It's a shame to hide those abs... This problem will be solved soon. Aha"] changed to ---> She puts her top back on and said: "It's a shame to hide these abs... This problem will be solved soon. Aha"
[You: "What did you said?"] changed to ---> You: "What did you say?"
[Tracy: "Nothing darling, I have to go, my.... Mom whant me to... help her. See ya!! I will have a little surprise for you when I come back!!"] changed to ---> Tracy: "Nothing darling, I have to go, my.... Mom wants me to... help her. See ya!! I will have a little surprise for you when I come back!!"
[Then she leave making her ass sway and making sure you can see it.] changed to ---> Then she leaves making her ass sway and making sure you can see it.