Hi Joe67
In my opinion, you made a mistake by writing a termination letter before finding an interested party willing to take over your business.
It would have been wiser to find a new tenant who wants to pay for your business and to take over your existing contract. Because in general a good lease contract is a part of the intangible assets of the business as well as a loyal client base.
Now, you have lost your rights to it. Once your rent contract has run out you will have to go and your landlord can do with the space as he wishes. In general you must also leave the space as you found it, i.e. take all the fittings out before leaving.
However, it is your right to stay there until the end of contract. So if their new tenant wants the shop before due time you may negotiate with him for some remuneration for fixtures and fittings money.
http://www.mieterverband.ch/zh_top.0.html
There is an association of the rentees that offer a well informed legal advice for free (if you are member).
.•´¯`•.¸¸.•´¯`°romainesol°´¯`•.¸¸.•´¯`•.
Good luck