“当我快要死了的时候”用英文怎么说？

while I am dying
be dying是很地道的“快死了”的说法
前面的副词应该用while，一般进行时都用while而不是when，虽然这个是进行时代替将来时，但形式仍是进行时~

When I have soon died time

when I was dying......

When I soon died time.

反正这是个将来时，用When（While) I’m going to die.或When/While I’m dying.

While I was dying