Fortunately I was just in time for the interview.翻译成汉语~~？？

副词作状语修饰整句话。

幸运地是我恰好及时赶上了面试。

也可以说

Luckily I was just in time for the interview.

幸运地，fortunately 充当状语成分。
fortunate是形容词。
幸运的是我刚好及时赶上应聘。

幸运的是 我及时赶上了这次面试