Classifieds / I will buy second hand scooter in Warsaw. Whats the procedure? [4]

Hello dear sir & madams. I have been living in warszawa for three years as a student. I have validated(still continues) visa and waiting my residence card. I will buy a skuuter this week in warsaw but I don't know what is the procedure of buying a second hand motorcycle. Could you please explain for me? What should i do? Thank you 🙏🏻