Welcome to the forum and Assalaam alaikum
You're only 12 eh?
Have you studied the Qur'an and the Sunnah? you're still quite young so it's understandable if you haven't. They Qur'an contains all the essential truths you will need to know that our faith is the correct one, and in doing so you will be find all the answers to those BIG questions.
But it takes study.
My advice is, make salaah regularly and ask Allah for guidance. These are now the final BIG days and nights of Ramadhan. Make the most of them young brother. Ask Allah to guide you and give you knowledge. Ask him to forgive you whatever sins you may have acumulated in your so far, short life. Ask away, HIS bounty is endless, and doesn't diminish...
...ask yourself, why do the elders always speak of Islam so highly? Is it because their life experiences have led them to understand it as truth through years of quiet contemplation of the Qur'an and their ability to read the "times" we live in? amongst other contributing factors?
The answer is YES.
You're still young, so brother, do not despair - hope is there.
If you sincerely want to know truth - make salaah and make dua, as much as you can.
Also, well done for joining here because of the reason you mentioned above - this shows us here that you want to know "truth", and that young brother, is admirable
keep ya chin up, ok? I like you already

masha-Allah.
Scimi