Why is "Would you like me to make coffee?"not accepted?
Because your translation is Conditional Mood, and the original sentence is not.
You want me to make coffee? should absolutely be accepted!
It's totally optional to use the question construction "Do you want me to...?" or simply use this: "You want me to...? This is basic English! It should not be marked wrong.
Do you want me to make a coffee? Why is "a" coffee not accepted?
It would be accepted usually, but translating literally, the phrase in portuguese does not have article.
this is surely one of those occasions when english speakers (especially americans) would say 'you want me to make coffee?' just like a portuguese speaker.
Do you want me to make you coffee?
There's nothing in the sentence to imply that the coffee will be shared or given to someone else - just like in English, you'd need something extra to convey that.
Would you like me to make coffee?
The usual sentence is : Shall I make coffee? which is not what you wrote in Portuguese but is a more common way to ask people about their desire or lack there off to have coffee!We also say do you want coffee?
Will someone please just make me a coffee... :)