Dought & clear - Nameemah (Back Biting to Destroy Relations) from a Kafir (Non-Muslim).

I am a new convert to Islam, and I have a Christian brother who lives with me.
My brother does not likea person, who used to be a friend, that helped
me to become a Muslim, and my brother told me some bad things about
that friend.
So I had a big fight with this friend and we don't talk any more. Did
I do wrong?
By the way this friend used to ask me "where I go?" and he used to
call me a lot.
Do you think it is wrong to cut my relationship with this friend? P.S.
I know that this friend likes me very much...And I think he is a good
Muslim.
Praise be to Allah.
Subhan Allah (Glory be to Allah)! How did you cut off your ties with
your Muslim brother because of some news about him that was brought by
a non-Muslim?
Allah says (interpretationof the meaning):
"O you who believe! If a rebellious evil person comes to you with news
verify it…" [49:6].
This person is not just a "rebellious, evil person" (fasiq), he is
also a kafir (non-Muslim), so how could you believe what he said and
on that basiscut off ties with your Muslim brother? Indeed, what you
have done is wrong, and you must go back to this Muslim friend,
because it is not permissible for a Muslim to forsake his brother for
more than three days. Since he likes you and was the reason why you
became Muslim, you owe him a great deal. How can you cut him off? Go
back to him and do not leave him unless there is some clear evidence
and proof that you should forsake him for some serious matter that
goes against Islam.
We ask Allah to grant us and you guidance and strength.