Re: Difference between I had Written and I have written
Welcome to the forums.
Past: I wrote something. I wrote it yesterday. Completed action, in the past.
Present perfect: I have written something I want you to read. The action is complete, but it connects to the present.
Past perfect. I had written something and shared it with a friend, and then I saw my writing with my friend listed as the author. I felt completely betrayed. -- Use this for a completed event in the past that comes before something else also in the past.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.