Hi Marek and welcome to the forum! I am of (mostly) Polish descent, but don't speak the language. Love your YouTube videos, and some words (yogurtu, minutach) are easy to follow.
That's great how you removed the whey by using a strainer. I never figured out a good way to do that (I've been using a cup, but then you always get some curds along with the whey), so that's a great tip.
-Lance