In my contract there is specified a penalty of CHF 2000 for not giving proper notice.

You could try and talk to them, and there is a good chance, they will agree, just to let you go, earlier. If you have another job, they can not force yo to come in. In my last company in scotland, they said, they would rather just agree to letting people go earlier, and then leave on good terms. They will probably do the same here, depending on how easy they can find a replacement.

Doc.