He has left Shanghai for three days already.这句子对吗？

不对
leave为短暂性的动词.
这样要用延续性的动词,因为for three days是时间段
可:
he has been away from Shanghai for three days.
or:
He left Shanghai three days ago.

不对，for three days是延续性的时间
而left是瞬时动词，
正确的应该是
he left shanghai three days ago.

不对,leave不是延续性动词,不能加表示段时间的短语

already的位置不对
应该放在has之后left之前

already- place is correct- well..i must say that this is correct from a colloquial view...

everyday language..the 'already' appears at the back

formal- He has already left Shanghai for three days.