How do I understand 的 in 因为广州的雨季下的那个雨真的是特别的大? So I am trying to understand the 的 in this sentence which came from a native speaker.
因为广州的雨季下的那个雨真的是特别的大。

Can any of the 的 (by itself) be eliminated without modifying the meaning of this sentence?
下的那:  If only these three words were removed, will the sentence still grammatically correct and retain its original meaning?
真的: If only these two words were removed, will the sentence still grammatically correct and retain its original meaning?
的大:  Is the 的 necessary?
因为 广州的 雨季 下的 那个 雨 真的 是 特别的 大。

Only the 的 of 下的 can not be removed.
No. Because the 个 must be with 那. You can remove 那个 ,  or replace 下的那个 with a single 的.
Yes. 真的 means trully.
No. But you should know that the 的 is belong to 特别.