i am currently a student又没有语法错误

语法上没错

只是从英语的习惯上来说 不太合适

可以换成如下表达:

1. Currently I am a student.

2. I currently am a student.

3. I am a student currently.

whatever you were looking for doesn't currently exist at this address. 为什么用whatever而不是what

whatever you were looking for：这是个名词性从句作主语。

whatever=anything that，因此：whatever you were looking for=anything that you were looking for, 即你在寻找的任何东西。

如果用what，虽然也是名词性从句作主语，但没有“任何”的意味，what you were looking for 即你在寻找的东西

所以含义还是有区别的。

currently 作为副词在句子中的位置很灵活，是可以放在exist后面的，意思不变。

不幸的是,他在火车站担心的等待了2小时。用英语怎么说?。

Unfortunately,he waited for two hours worried at the railway station.

Unfortunately 副词修饰整个句子。

wait for ... 等待

worried修饰主语

at the railway station 作地点状语