I have applied for temporary residence permit for studies because of continuation of my studies in Poland. Can I perform work (e.g. under civil-law contract)?

If you are a full-time student and you have a valid visa or valid temporary residence permit you can work without work permit. BUT  if you are a full-time student and you work, we might not grant you the permit if there will be any doubt as to the reliability of your declared purpose of stay in Poland. In order to avoid this situation, always remember to indicate your main purpose of stay in Poland in the application form. If work is your main reason of your stay in Poland, then you should change your application to be dealt as temporary residence and work permit.