What you might want to do is go for an exclusive agency agreement
If you are going for an exclusivity agreement. Go with these guys perfectproperties.home.pl/index.php?pid=18&lang=en. Just to give you an indication your place in Nowy Wilanow the going rate is around 6-7,000 Zlotys per meter in this market. The price in Mokotow depending on building/location is around 8/9,000 meter
/or getting higher offer prices.
It is not really a time for achieving higher prices more just to get out, expect to be squeezed buyers want to smell blood.