Basically it is what Peter has said - the pipe seals have failed - and that means the front of the engine is coming off - expensive enough on a normal N62 but with the supercharger also needing to come off - then be mounted again correctly and the timing set properly this is far from a cheap repair.
Prices in the US are 8-9000usd - which could equate to 12-15k in Switzerland (higher labour rates) - and that is before any Alpina specific parts - and/or damage to the internals of the engine. On a car worth around 30k CHF it is getting dangerous close to it writing the car off!
