Most of the advice we have about asking for help on homework or self-study questions, or other questions of a similar nature, is encapsulated in our homework policy post. So I'd suggest taking a look there.
Probably the main point you should take away, when it comes to improving your questions, is that when you have a homework/self-study/etc. problem, the question you ask on this site should not be the question asked in the problem itself. Similarly, don't ask things like "how should I start?" or "what should I do next?" or "what am I doing wrong? or "can someone explain this?" Those are all too vague and broad to be good questions for this site.
What we'd rather have you do is narrow the question down to one very specific issue that you want to know about, ideally something that other people might also be wondering about even if they're not working on the same problem you are.
You may find that some of the questions you want to ask while preparing for an exam like the JEE just aren't suitable for this site - that is, that you can't figure out any way to phrase the question in a way that meets the guidelines I mentioned. Sometimes that happens, and we accept it; this site is not trying to be a home for every physics-related question a person could possibly ask. The community maintains a (non-comprehensive) list of other sites where you might be able to find some help with things that aren't on topic here.
As far as deletion... the system only lets you delete your questions under certain conditions.
You can't delete your own question when it:
- has an answer with upvotes (even if it has a net negative score)
- has an accepted answer
- has multiple answers (even if there are no upvotes)
- has an answer with an awarded bounty
The moderators generally agree with the criteria used by the system to decide whether to show you a "delete" link at all, so our approach is that if you see the "delete" link there, feel free to use it. However, deleting posts will not help you get out of an automatic question ban. If you find yourself in that situation, I would advise against deleting your posts. Instead, focus on coming up with a good question to ask next time you get the chance to do so. If you have access to [chat], you can ask people there for advice on how to ask a good question.