Is Bitcoin a currency produced by someone or something?
If yes, then what will happen if the production stop?
What is the purpose of the 21million limit to Bitcoin mining?
And finally WHAT IS IT FAITH AFTER REACHING ITS LIMIT
I would recommend you to read all the original material that Satoshi Nakamoto wrote himself, starting from the whitepaper. That will give you a clear answer to all these questions.
Here's a website that provides links to all the emails, source code, and posts that Satoshi did when creating Bitcoin: https://satoshi.nakamotoinstitute.org
Once you read them you'll understand Bitcoin much better than the vast majority of people.