As wvboxst3r stated about the horn issue, I would look at replacing the airbag retaining frame in the steering wheel (under airbag) and as stated disconnect battery and wait 15 minutes before attempting.
If your horn never worked and was missing the relay, it could point to someone experiancing the Horn issue where when you apply your brakes the horn would honk, some people as a work around to not replacing the frame would place paper over the contacts, creating some rubber groments to apply or remove the relay to prevent the horn from working.
I myself had to replace mine and not a big job to do, there are quite a few post on the subject here and the part to replace I am talking about is here:
Airbag Retaining Frame:Porsche Parts & Porsche Accessories - Wholesale Porsche Parts & Tequipment - Cayman Panamera Cayenn
good luck
Monica
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