Why do Polish children master it so easily?
All languages have their difficult and easy points. When asking if one is difficult, the question should be, difficult for whom?
One issue is that unlike French and English which have many second or third language speakers who are not expected to speak it perfectly, Polish is usually for its natives who aren't used to hearing mistakes. That will doubtless change with time, as the language and its use evolve.
Nevertheless, it's possible to pick it up by speaking; it's often the best way since those who teach it aren't usually that skilled in teaching languages.
Get over it.
what is wrong with t
They look fine to me.