Rewritten. "No person has ever given me this before. It is the first time in my life." ---“任何人曾经给了我这个之前，这是我有生以来第一次。" I hope this helps. It is to say that whatever was done, That individual has never received the item from anyone before. You are the first to give them it, whatever "it" is.

okay,thank you!

The clause is used to modify the word "time" (object of the main-sentence "this is X"). And the clause itself is appositive to its onwer, "(the first) time".