Real Estate / About terminating my flat contract in Poland [23]

Hello,
So i have a contract with my current flat owner and im planning to go back to my country for next semester but i have a problem. On my contratct i have this "if sublessee wants to quit contract before settled terms, he shall use his best effort to find another sublessee" part and im trying my best to find someone but no one wants to move in. I talked with the owner and he said even if you leave the country you need to pay me rent until the end of our contract. So thing which i wanna askis, is this even legal? What can i do about this? Because i really just wanna leave and go back to my country. No way im gonna pay this guy until the end of my contract. Even if they take this serious and go to law court,what can they do?