Taxes when teaching online while living in Poland

Cześć everyone and thanks in advance for your help.
I'm a European citizen and have been living in Poland for 2 years. I'm a language teacher for a local school but recently I've also started giving private online classes on websites such as preply and italki, for those of you who know them. They're websites where you create a profile, students from around the world find you and the lessons are made on the platform (and the platform keeps a percentage of what the student has paid you).

Since I'm starting to work more and more with these, I was wondering, how does it work with taxes? How should I declare these earnings? And if I stopped working for my school and did this full time, what legal procedure should I follow?

Dziękuję bardzo

you should teach preppty kids and go to preppty high end private schools and just live the preppy life and not worry about taxes.

Unfortunately, Poland is a country where for mamy decades communists had laws in place which encouraged people to break laws. How? By making laws hard to follow, absurd, and toothless. In 2016 I had a local government admin person advise me on my specific tax situation, which BTW their office had created be giving me wrong information, that I should falsify and submit another government form. What can you do..?You can go to the local Tax office and describe your business. See what they tell you. Take names, dates. And keep them in case you get hassled in future.