okay thanks!! it's great that you helped me!!

hi ,lily,my name is Laura.first i want be your friend ,and teach you chinese. Then about you sentences :
你好我叫美丽莎。this one is OK!
我是法国人你呢。if you use a comma between 人and你 it will be better.
我住在perpignan。this one no problem
我是学生和我一十八岁。please change it to two sentences as:我是学生。我十八岁。as i'm a student and i'm eighteen we don't always say together use 和 to put them together. another point for you, we nerver say 一十八岁,we only say 十instead of 一十for oral chinese.but we will say 二十，三十and so on.
在普通话里我们通常只用“我”表示自己，but we have a lot of way say “我”in our dialect . if you don't want see so many "我”in you sentences just leave same of  them out. so your sentences can be say like :你好，我叫美丽莎，是个法国人，你呢？我住在perpignan，是个学生，今年十八岁。
if your want to learn more please contact me. send e-mail to me([email protected])

hi 
i'm kungko from China
i live in hangzhou, it's one of the most beautiful city in China
maybe i can offer some help in your Chinese learning 
and also i want to know more about France (it's really a charming country)
by the way, l love the movie "Amelie" so much
 

sorry i keep saying "我" but i don't know if i could say it in an other way (like in japanese)