why do i hear a strange sound when she says "chléb"?
The TTS is not perfect. It is a computer, not a human.
Czechs usually ask question in negative form. For this reason, I think one of the acceptable answers shall be: "Do you eat bread?"
No, that is not true. Czechs use negative questions when offering something politely, but that is not happening here.
OK. Then one more question: Is "Don't you eat bread?" another answer or isn't it accepted? If not, why?
"Don't you eat bread?" is accepted.
The intonation of the sound is affirmative while there is a question mark in the answer
True. The TTS is not perfect.
Its but this sentence is a question