Dear Caroline,
yes you must paid CGT and there are more duties. If you need help, please conatct with us at the mail info@chudzik.pl. You can tell that you are from the command of Gregory and speak with Noemi.
We are from Lodz in central Poland, but works in whole country. We can help you in such transaction, and have tax adviser who can help you carried out this transaction in most convinient way.
If you have any questions please let me know.