Okay then I'm quite confused about this, it's my understanding that mujhe karna hai = I have to do, mai karna chahta hu = I want to do, mujhe karna chahiye = I should do, mujhe iski zaroorat hai = I need this, mai ye chahta hu = I want this, (mujhe ye chahiye I don't even know about, too many translations) but apparently so many of these also mean many others. I've heard chahiye being used as both Need and Want in addition to Should, I've heard chahta being used as Like (mujhe pasand hai usually, na) in addition to Want, karna hai being used as Want to do, or even Like to do, in addition to the base Have to do, and when I ask people about the actual definitions of these sentences, everyone seems to give me a different answer, like chahiye, some people have told me it means Should, some say it's Need, and some say it's Want, and when I tell people others have given me different answers they tell me that person was wrong, or that maybe their Hindi is not great, is this a regional thing? Like maybe all of these phrases share the same definitions of want, need, should, like, and are just interchangeable based on the region and how Hindi is spoken there? It would be nice to get definitive answers on these, maybe the way I've learned them is wrong, or maybe there is just some flexibility depending on what kind of Hindi you're speaking. Any help would be appreciated, thank you.
Let's go over this one by one:
i) verb infinitive+है: This is a colloquialism that you will not see in formal/written Hindi. The meaning (have, want, need or should) purely depends on the context. For instance, 'मुझे जाना है' can mean 'I want to go' when it's said a child insisting on going to the movies and 'I have to go' when it's said by someone who wants to take your leave at the end of a party.
ii) चाहना: The verb चाहना and all its forms (excluding चाहिए) mean 'want'. But there is no immediacy involved in this 'want'. Eg: मैं डॉक्टर बनना चाहता हूँ is talking about my future plans, मैं पैसे चाहता हूँ just means that I want money not that I want or need it right now. Because it represents a general rather than immediate desire, it may be used as 'like' in some instances. Eg: मैं आपसे कुछ कहना चाहता हूँ = I want to tell you something = I'd like to tell you something. This also happens when the object of your desire is not something you can really 'possess' (like another person) in which case 'want' doesn't make sense. Eg: मैं नेहा को चाहता हूँ =I like Neha. This usage is what gives rise to the noun चाहत which is desire/love. Used like this, it is a synonym to पसंद करना but चाहना with a person usually specifies that you like them romantically whereas पसंद करना is ambiguous.
iii) verb+चाहिए: This is best translated as 'should'. However, it is also used for obligations when 'need to' is more appropriate. It never means 'want' or 'desire'. Eg: मुझे जाना चाहिए - I should go/I need to go.
iv) noun+चाहिए: This is a stronger form of चाहना. It may either be a more intense desire (i.e: need) or one with more immediacy. You can think of it being midway between चाहना and ज़रुरत (which is always 'need'). Eg: मुझे दो केले चाहिए -I want two bananas (as in I want them right now), मुझे पैसे चाहिए - I need money.