Besoin d'aide lettre anglais

Bonsoir tout le monde,

Je suis actuellement en première.
Cette été je pars en séjour linguistique au usa dans une famille d'accueil et pour cela je dosi écrire une lettre de présentation afin de meiux "cerner" ma personnalité , cependant j'ai des petits soucis..

En effet, je ne suis pas tres forte en langue (je part la bas pour m'améliorer ) , je n'arrive pas a ordonner mes idées et a en rajouter , et pour finir la grammaire etc.. laisse a désirer..
Pouvez vous m'aider ?

"Dear sir,

My name is Laura, im 16year old.
I leave in the south west of the france, with the beach and the mountain.
Im in the sixth form ,in economics & social option english . Later, i would like to be humanitarian worker or working in the the commercial negotiation.
Even if, my marks in spain and english are not very good I do the best i can because my dream is speaking a lot of languages, to understand and share with all the people in the world.
Ive got one little sister whos 13years old, we re very close, she is an artist
My main passion is my friend, doing party to the sea side all the night, dancing until not be able to, just be with them eating chocolate..
My friend are very different: dancer, a nigerian, bresilian, surfer,

I am a highly energetic self-starter, indeed im keen on travel to meet new pople and differents culture, to share my viewpoint.
Since 2years i play guitar, one hour a week with a great professor who makes me discover a lot of bands who have seen in concert: Cocoon, Placebo, jack johnson.. Besides, generally i like all the kinds of music: pop, rnb, rock, reggae ..
I go to the cinema around once a month, my favorite movie is Into the wild, because its an adventure film about a travel in USA !
Photography, sports, shopping.. People around me say im a jack of all trades.

It will please to me to meet you to discuss it more.
Please accept the expression of my best greetings."