A translation (by me) for those of you not blessed with a fluent comprehension of Polish - to explain why this scene is hilarious.
The little girl first complains that the bread is sliced too thin. Then too thick (see, I lost two teeth). So the man asks what thickness the bread should be. So she indicates, "taka", this thick, with her fingers.
After that she complains there's too little butter. "Too little?" Yes, too little, she replies. Why do you act so surprised?
The girl then narrates in the voiceover that this is how her adventures with the monastery of weirdos began, etc.