<ol><li>留学生= International student 外国学生= foreign student. For example, Wang is a Chinese, he studies in America, so when Chinese talks about him, he is a 留学生 but he is not a 外国学生. However, if American talk about him, he will be both 留学生 and 外国学生.</li><li>Normally, we say 他认识了一个漂亮的姑娘. It's same of English grammar. 一个=a, 漂亮的=pretty</li><li>可能=might 会=will</li><li>想=want 要=be going to. However, in some cases, it also can be different.</li></ol>