In order to do so, I need to sit to the theory exam in Poland,
You can do the Theory in any EASA State, bear in mind however that each State sets its own exams so they will be different in each State as will the language. You need to contact either a DTO or ATO in that State and arrange to take the exams. The National Authority is required to publish a list of DTOs and ATOs. Make sure that on completion you have a Course Completion Certificated appropriately signed and authenticated.