Hello Yusuf, I have some proposes to your practise. I highlighted them in red. Good luck to your chinese learning :)

你们好啊~~
我的名字是尤瑟夫。我是摩洛哥人。我在马拉喀什。我今年21岁。我是学生。我的母语是阿拉伯语。我的第一语言是法语，英语是我的第二语言。我正在过暑假。我要学汉语。我能教你阿拉伯语。我使用法语和英语与人们沟通。 

That I wanted to say :
Hello everyone.
My name is Yusuf. I am Moroccan. I live in Marrakech. I am a student. My native language is Arabic, my first language is French, and my second language is English.
I am in summer vacation. I want to learn Chinese. I am 21 years old. I can teach you Arabic. I use French and English to communicate with people.

Actually, there is one thing that I haven't understood. When you say "my first language is French", I think it indicates "my first foreign language". If my understanding is correct, the translation should also be changed.

Dassin is right, first language means your native tongue. In this context, I would say your native language (母语. Did you try to use the word本族语? That is rarely used) is Arabic; French and English are your second and third language. 

practise

你们好啊~~
我的名字是尤瑟夫。我是摩洛哥人。我在马拉喀什。我是21岁。我是学生。我的本组于是阿拉伯语。我的第一语言是法语，和英语是我的第二语言。我在暑假。我要学汉语。我能教你阿拉伯语你。我与人们使用法语和英语与人们沟通。
That I wanted to say :
Hello everyone.
My name is Yusuf. I am Moroccan. I live in Marrakech. I am a student. My native language is Arabic, my first language is French, and my second language is English.
I am in summer vacation. I want to learn Chinese. I am 21 years old. I can teach you Arabic. I use French and English to communicate with people.

practise

你们好啊~~
我的名字是叫尤瑟夫。，我是摩洛哥人。我住在马拉喀什。我是21岁。我是个学生。我的本组于母语是阿拉伯语。我的第一二语言是法语，和英语是我的第二三语言。我在过暑假。我要学汉语。我能教你阿拉伯语你。我能与人们使用法语和英语沟通。
That I wanted to say :
Hello everyone.
My name is Yusuf. I am Moroccan. I live in Marrakech. I am a student. My native language is Arabic, my first language is French, and my second language is English.
I am in summer vacation. I want to learn Chinese. I am 21 years old. I can teach you Arabic. I use French and English to communicate with people.