Is there a colloquial/slang equivalent for "What's wrong with it"? And that, is "what's wrong with it" an informal question? If so, how do you say the same thing in a formal situation? Thank you in advance for kindly answering my questions!

How to address a teacher in class, for example when you have a question? Can I tell "excuse me Sir" if the teacher is male. How can I address a female teacher , I should call her Ms. or what? What about university teachers?

We have no classes next session vs We have no class next session? As a teacher if one wants to tell the class that next session the class is canceled, shuold she/he use the singular noun "class" or the plural form "classes"? If "classes", can you please explain why? I mean just one session is canceled so logically we should use the singular form, shouldn't we?

Can we use would in this sentence: "I would see a great jacket, but you wouldn't let me buy it."? According to Passages 1 book- a book for learning English conversation- when we use would to refer to past habituals, we cannot use it with stative verbs. As far as I know see and maybe let- I am not so sure about let- are stative verbs in this sentence. Now this the question: Can we use would with stative verbs in such sentences referring to past habituals? P.s. the sentence is an example sentence in the book, unit 9, lesson B. P.s.2: the context of this sentence is an e-mail to a friend who is moved away. And the e-mail sender is talking about things they used to do together and so on. Thank you all in advance for all the time and effort you spend to kindly answer me. :-)

word request (adjective) What is the proper adjective for an act or work that needs sacrifice, selflessness, and devotion? We cannot say devotional because it is used in religious services, according to Merriam Webster's. So how do you define such an act, or work? Thank you all in advance.

How do you ask a question whose answer is "I'm the second child in my family"? When we want to know the same information about presidents, I found out we can ask "what's president x's presidential order number?" But I cannot find how to ask the same question about other things. In my language we have a pronoun, chandomin, that we use for asking these kind of questions, but it seems English doesn't have such a pronoun. So how do you ask these kind of questions? Is it natural to ask for example,"what's your birth order number?", or "what's the order number of the book you chose?, imagine you were supposed to chose a book between like 20 books.". Or maybe you use different types of questions depending on different situations. Like asking "which book did you choose?" and "how many older siblings do you have?" Thank you in advance for your care and answers.

Word request Some people do not have the capacity to be wealthy. Is this sentence correct? I mean can I use "capacity"? What I mean by this sentece is that if they have a lot of money, they will change in a bad way. Like they may become arrogant, greedy, even fall in love with their wealth and find it hard to spend it, or even become a too selfish person. In my native language we say the person does not have the capacity for wealth. What do you say in such situation? The question formed in my mind when I was talking about weath with one of my colleagues and I used this word then doubt if I used the correct one. Thank you all in advance for your answers!

I'm good at dance vs I'm good at dancing we can say, "I'm good at chess/playing chess".Here is my question: Can we say, "I'm good at dance.", or I should only use "dancing"? I f I should only use dancing, can anyone tell me why?