Generally speaking the economy does not have a huge effect on the boyancy of the used car market, barring a full-on recession, particularly with a luxury car such as the Porsche Macan. Even if market conditions results in used car prices firming up, it is unlikely to result in the market value of your Porsche going up - it is a used car and its value decreases with time, so there is little to be gained by waiting for the economy to improve.

How you sell your car is a matter of balancing the effort you are willing to put in against the selling price you want to achieve. Selling privately would likely get you the best price, but would require you to place an advert and deal with any enquiries. Using a local dealer or an car-buying website would be a lot less effort but would mean a smaller return.