Unfortunatately, there are still huge gaps in the logic of the whole story. That is why I still claim it is not Poland, but Turkey and you translated somebody`s old post from Arabic into English. Ha!
All who believed it are old fools. hahaha
I arrived to find that the property has not been cleaned and is filthy
So, your arrived at the property alone, without the landlord or the agent who had arranged the place to you. In Poland the agency representative always travels with the client to the new location. Where did you get the keys from? Strange.
I have replaced it only to find the area has terrible reception
The outskirts of Gdańsk and terrible reception in middle class surroundings. Strange.
You also said a few contractors/professionals have come to see the house. How did you communicate - did they all speak English?
Why do you seek amateur help in a discussion forum if consulting an English speaking lawyer in Gdańsk on this matter would cost you maximum 200 PLN?
What is this real estate agency you used? Tell us its name and I will call them and ask if they really perform such scams on foreigners. We will know within a few minutes if this is true or not.