The other gospels not part of the Bible AFAIK the the writers of the NT are only Matthew, Mark, Luke, John, Paul, James, Peter and Jude. 

The writing of the other apostles, Andrew, Philip, Bartholomew, Thomas, Matthias, Simon abd James why are they not included as a gospel of the Bible?

I mean, according to the Bible they are inspired by the Holy Ghost and their writing must be also a source for truth, why are their writings or teachings not included at all? 

And who is the author of Hebrews in the NT?
There are two matters wrapped up in this question.  Let me take them one at a time.
1.  How were the components (&quot;books&quot;) of the NT Chosen?
The various books of the NT were chosen by the early church, essentially by consensus - they were clearly inspired and some published lists of these books.  Various church councils then put an official imprimatur on the final list.  The requirements for inclusion was always the same - a NT book had to have been written by a person who witnessed the events they recorded or at least spoke to the person who did.  All the current NT fit this criterion.
2.  Why were some writing excluded?
There are many writings that have been excluded and these fall into two broad categories:
(a) Writings of pious, Godly men who were not apostles or associates of Jesus such as, the writings of Clement, Polycarp, Hermas, etc.  These writing do not claim to be inspired and they might have been shocked to hear that their writings should be included in the Canon of Scripture
(b) Forgeries - writings of those who pretended to be someone else famous.  The Greek term for this is &quot;pseudepigrapha&quot; - a writing with a false title.  Nearly all in this category were written in the second century (or later) but masqueraded as though they are written by someone in the first century, an associate of Jesus.  These include: The Gospel of Mary, The Gospel of Thomas, The Gospel of Peter, The Gospel of Barnabas, and many more.
I make no comment about who wrote Hebrews - that has a huge literature and I do not intend to extend it.  I refers the reader to some of that material elsewhere.