I have a 2000 Audi A6 2.7 Quattro and just recently my car battery randomly dies. I received a jump and afterward, whenever I start to accelerate the rpms just rise and the car slowly speeds up. I have also noticed a funny smell coming from the engine whenever I park the car. With in a day the condition got worse and now whenever I lay off the clutch the car has to rev up to 4000rpms to move the slightest bit.

I want to know what could possibly cause the issue and where is the clutch master cylinder reservoir is located?

 

Sorry to tell you... but your clutch is toast. The smell you get is coming from the clutch disc. Don't breathe that stuff... Asbestos!!!
At this stage your only recourse is a new clutch since yours has been slipping for a while now. Don't use the car as it will leave you stranded...!