1）我会在30分钟内到达图书馆 2）我原本准备在今年的春天的时候去中国学习，但是我的想法改变了，因为我想首先得完成我的主修课程里所需要的要求

1) i will go to the library in 30 minutes 我将在30分钟后去图书馆 2) I was originally going to study abroad in china this springtime, but i changed my mind and decided to go study abroad in china in the summer; because i just wanted to finish the requirements in my major first 我原来打算这个春季去中国学习的，但（后来）改变了主意打算夏天去中国学习，因为我想先完成我主修科目的课程要求

1，我三十分钟后去图书馆。 2，我本打算今年春天去中国学习，但我改主意了，决定今年夏天去。因为我想先完成我专业上的学习任务。

1) i will go to the library in 30 minutes/我将要去图书馆在30内，if you according to the word in translation is such,but in English,about time word used to be in the back,so it is 我将会在30分钟内去图书馆。 2) I was originally going to study abroad in china this springtime, but i changed my mind and decided to go study abroad in china in the summer; because i just wanted to finish the requirements in my major first/我原本打算今年春天去中国留学（notice the time sequenc），但我改变主意决定夏天去中国留学，因为我首先想完成我主修课的要求（the first is placed in the last,but in Chinese is in front）