Whenever I ask a question that is found to be duplicate. If I search the question previously to make sure it was not asked before it does not appear as the language of me and the question is not the same. So how can I stop asking duplicate questions?
I took the liberty to look at your questions, and I can see a lot of one-liners there. I suggest you research the question you're about to ask yourself, and show that research in your question. If you do that, you'll more likely find similar questions (with answers) or find the answer yourself.
Other than that, getting some level of understanding in topics you're interested in really pays off. E.g. if you're interested in black holes, read a book about them before asking questions: most of the basic questions you may have will be answered there, and the remaining questions will be a much better fit on Physics SE.
I suggest paying attention to, and reading some of the suggested questions that pop up when you start to ask yours (I know this feature exists on the desktop site, maybe not mobile).
This is an example from when I type in a new question with the same title as your question from today; which is gaining some votes as a duplicate. I actually flagged this one as a duplicate; so I can walk you through the process for how I found it, along with the process you could use to find it.
You can already see, there are some suggestions here for questions which may contain your answer. The first link is your question, which it should be, because it has the exact same title; so the system is taking a guess that it could answer your question.
As another sample, the question on DC current through a capacitor, I can demonstrate the same technique:
You can see the link below your question is what your post got marked as a duplicate of.
I will say, you can't apply this to all your questions. These ones are really low-hanging fruit, where the duplicate is quite obvious.
For others, such as your black hole question, you may just need to think of other ways the question could be worded.
It also seems as though you don't show any research of your own when asking these questions. Generally, it's a good idea to try and look up answers on your own first. Not just on this site; but other places as well. Then you can narrow down what confuses you, and possibly find duplicates worded in ways that you wouldn't otherwise expect.
Before asking a question:
Use the built-in search engine to search for duplicates.
Alternatively, search the Phys.SE site with an external search engine, e.g. Google.
When asking a question:
Pick a good title which captures your question in one line, preferable in the form of a question. The SE software will then suggest possible duplicates.
Fill in relevant tags to further help the SE software.
My two cents:
You should search for duplicates before asking your question, but the built-in search engine is really not that good for this task. Doing a google search for your question with "site:physics.stackexchange.com" at the end of your query is a superior way to find duplicates on this site.
Compare, for instance, my search for duplicates to this question:
The query isn't perfect, but the Google search, unlike the site search, immediately brings up relevant results.