Hi, Erwan. I think you should have posted this under 'Answers' on italki, but I'll answer your questions below:
* "Hi" = Can you tell me in which different way you can say it (i know geia sou and kalimera, kalinikta) ? In France we have many different way to say it ==> Γεια / Γεια σου / Γεια σας (=polite form) / Χαίρεται (= polite and old-fashioned)
* Same for "How are you ?" ==> Τι κάνεις; / Τι κάνετε ; (=polite form)
* "Hi ! My name is Erwan, I'm 17" ==> Γεια! Με λένε Ερβάν, είμαι 17 (δεκαεπτά).
* "I'm from south of France." ==> Είμαι από τη Νότια Γαλλία.
* "I really love the Greek language due to his beautiful sound and hand writing" ==> Μ' αρέσει πολύ η ελληνική γλώσσα επειδή έχει όμορφο ήχο και όμορφη γραφή.
* "I start to learned it since 4 month by myself" ==> Ξεκίνησα να τη μαθαίνω μόνος μου πριν 4 μήνες.
* "Where do you live in Ελλάδα;" ==> πού μένεις στην Ελλάδα;
* "Do you learned french ?" ==> ξέρεις γαλλικά;
Efkaristo para poli...
παρακαλώ! :)
* "for your help"