No i do not believe. You don't change it just because you say that i believe in not believing.

There is also a clear definition for it:

"Believing is the mental act of accepting something as true, real, or correct, often without requiring absolute, physical proof."

I'm absolutly fine saying that I don't know something. I do not know a god exist, or multiply etc. But honestly that question comes down to me more like "Does randomess exist".

Yes its absoutly a religios thing that homosexuality is bad. You call it yourself 'sinful relationship'. Its not a sin just because church doesn't like it. Also plenty of religions are responsible for making it a sin outside of religion.

And yes if the church condonse all sexual practices, it does include homosexuality and makes it a church doctrine.

> Christians don't believe in this because a book written thousands of years ago say so but because deep in their souls it makes sense and is the truth for them.

Sorry mate, but that's just cultural indoctrination that made them feel that way, and the culture is intimately tied to the book.