[RichDad]

I know.

The Christians believe in first cause. That means all things were created by a higher power.

Buddhism eschews this belief but does not offer any explanation for why we exist, why the earth is there, why there's a moon. 

It identified the reason for why we suffer and summarized that in the 4NT. This suffering is in our inner self which you can call soul or spirit, whichever you prefer. But it cannot explain why the body suffers from pain due to diseases.

No one can explain all these things... yet.

Religions were started to try to answer these mysteries of life but in fact they are just creating a new problem to solve an old one.

Maybe Buddha was right, no one knows so don't ask.

If Christianity is the right one, then why are there so many other religions? The other people are stupid or what? Can't be, right? There are very smart, intelligent believers in all religions. There are also very smart non believers.

I can only conclude that no one knows the answers as of now. Those who say they know are the most ignorant.

If and when Jesus returns and proved to the world he is the creator , then can you say that Christianity is the right one.

You can claim that Christianity has all the answers to life but that is only your claim and belief. It is not a fact. Any one can make claims, no big deal.