"quieres comer" forms a phrase where both verbs are linked together, as this is the case we conjugate the first verb and the second verb remains unchanged, it is similiar to english where we would say "He could go", "could go" forms a phase so we do not conjugate the second verb i.e. we dont say "he could goes"
I know they want to teach us comer but... people just say do you want more bread. No "to eat"
It depends on the situation again. “Do you want more bread? (or something else) Or shall I get you dessert?”
“Do you want to eat more bread?” (or do something else with it) Or shall I save it for later? (I am not offering you more bread to take home to your dog.)
In Spanish they can also say “¿Quieres más pan?” which would actually be “Do you want more bread?”
That would be "¿Te gustaria comer más pan?"
"¿Quieres...?" is "Do you want...?"
"¿Quisiera...?" is "Would you want to eat more bread?" which is almost the same thing as your suggestion.
Can you just say : ¿Quieres más pan?" It looks obvious the bread is for eating and not for making bricks
It is not necessarily the same thing. I could want more bread at the store to make something with it for a party.
Do you want to eat more bread or do you want to take the rest of the food home?
Yes if you put the accents on tú and más, and “¿Quieres tú comer más pan?” would also be correct, but Spanish usually drops the subject pronoun so you would be emphasizing “you” as opposed to someone else. “Tu” without the accent actually means “your”, so without the accents, no, it would not be correct.
The suggested answer is awkward in English. It's far more polite and gentile to say Would (or will) you have (or want) more bread?
Same in Spanish “¿Te gustaría comer más pan?” is “Would you like to have more bread?” (“Have” meaning “eat”)
“¿Quisiera comer más pan?” is “Would you want to eat more bread?”
Also accepted, and more common in the U.S.: Do you want more bread to eat?
That is not quite the same. "Do you want more bread to eat?" (I have more bread that I can offer you.) "Do you want to eat more bread?" (Are you done eating? You aren't going to finish that?)
That is actually an imperative form that has been modified by the kind of verb that it is. "Do you want to eat more bread?" is the standard form and should be used when writing something down.