Translation:I want breakfast in my room.
"I want the breakfast" may be correct, but it sure sounds awkward to me.
In English we say "I want breakfast." If we were to say "I want the breakfast.", this implies that there is only one when in fact you can't put a quantity on it.
Well, unless there was already a specific breakfast being discussed. After "we have prepared you a full english breakfast" you could certainly answer "I want the breakfast in my room"
Perhaps if you were to be picking from a menu; "I will have the breakfast", along with Abshannon's explanation elsewhere on this thread.
I translated this to be "I would like breakfast in my room." Why is that not acceptable?
I don't see any reason why it wouldn't be accepted. All I can think is that "I would like" is a modal of possibility whereas "I want" is a modal of certainty. So, maybe they want the definite option here.