I think at least half an hour.至少要半个小时.
If you want to study English very well,you must put your heart in it.You can read anything concerned English.The words,the sentences,the news and so on.
如果你想学好英语,你就要用心.你可以阅读任何和英语有关的东西.记单词,背句子,看英语新闻.比如说设置英文网站为首页,生活中电视上看到单词就记的话,你其实不知不觉的就在学英语,而且还在用英语了