我来自阿尔及利亚。
我是从阿尔及利亚来的。
If somebody ask you " where are you from?",in Chinese it can say "你是哪里的"or“你是从哪里来的”。
Then you can reply "I am from algeria",in Chinese = 我是阿尔极利亚人 or 我是从阿尔极利亚来的。
If they ask you "where do you come from?",in Chinese it would be "你从哪里来？"
Then you can reply "I'm from algeria" or "I come from algeria",here the Chinese would be "我从阿尔极利亚来" or "我来自阿尔极利亚"