Yes. Your teacher is absolutely correct. You can say "I wish I had more time" or "I wish I could have more time", but you cannot say "I wish I would have more time". The example you found in your dictionary, "I wish you would be quiet", describes a completely different situation. Note that this wish refers to an action on the part of ANOTHER person. This of use of "would" indicates an action on the part of the person addressed. The statement "I wish you would be quiet" is equivalent to saying "Please be quiet". In other words, the speaker is asking the other person to do something. Similarly, "I wish John would visit more often", refers to the possibility that John might decide to visit more often. "Would" in this sense relates to the original idea of "will" meaning a voluntary action. By contrast, an expression of dissatisfaction about one's own lack of time ( "I wish I had more time") has nothing to do with voluntary action on the part of another person, so it is NOT possible to use "would". You should have more faith in your teacher!

Your teacher is correct. "I wish" is followed by past simple when you talk about yourself. The sentence you saw in the dictionary is different because it involves two people: you and the person you wish were quiet. When the wish expressed concerns somebody else, you can use "would". Su.Ki explained all this in more detail.

Both you and your teacher are correct, but everything depends on what you mean exactly, what period of time your regrets are about. The formula is the following: If you regret about present: I wish/if only I + past indefinite If you regret about past: I wish/if only I + past perfect If you regret about future: I wish/if only I + would + infinitive So, your example is a regret related to the future, while your teacher's example is a regret related to the past.

Thank you, Wei. I think you've phrased it very well. It is about capability (on the part of the speaker) as opposed to willingness ( on the part of another person). That is why you can use 'could' in this sentence but not 'would'. ""I wish I would..." is simply wrong.

Just to weigh in, I agree with Su.Ki.'s answer. I can't speak to whether it's strictly grammatically correct or not, but I can't imagine any situation where a native speaker would say "I wish I would have more time." "Would" used here seems to indicate "willingness" to me, so using "I wish" with "I would" seems contradictory. Your example "I wish you would be quiet" means you wish the other person is willing to be quiet. You wouldn't say "I wish I would be quiet" because you're in control of your own action. You could say "I wish I COULD be quiet" because it speaks to capability, not willingness. I don't know if the sentence structure "I wish I would..." is always wrong, but it doesn't make sense to me here.