Hello Omar,
Sorry to hear of your problem.
I think all those who have responded are really asking - have you asked the Audi dealership to give you a report on what has actually happened to your engine and why? The answer must be with them and to simply say it requires a new engine is not enough, and I don't believe a meaningful advice will be had via. the forum until you have that report from them. Whether you understand that report doesn't really matter, but need it you certainly do. Personally, I would not be content with a verbal report, but an e-mailed one would be acceptable - which you could then post on here.
It might be interesting to know how long you have owned this car, and whether it has a documented service history, and when it as last serviced. We take it the car has not been subject to recall in the recent past.
"Causation" . Any chance you are in the legal/insurance claim business? Not a term often used on here.
Kind regards,
Gareth.