Welcome to the forum Moin, sorry to hear your having issues with your Audi.
Youll find the members on here are a friendly bunch and will help you where they can :)
i cant help with all problems I'm afraid but problem 3, the whistle at high revs could be the turbo. There could be a gasket loose or pipes leaking. Worst case scenario if it is turbo related is a new turbo maybe required.
Sorry I can't help more.
Cheers
steve