There is no sin God will not forgive. All sin is forgivable. All one needs to do is ask and they shall receive forgiveness if they truly ask from the heart and they do so with a broken and contrite heart.
never, ever, say that God will not forgive a sin.
For Christ died so that Whosoever believeth shall not perish but have everlasting life. Jn 3:16
Even homosexuality is a forgivable sin.