Welcome to the world. These questions have been asked by nearly everyone with 3 digits in their IQ. Keep thinking, there are more.
Philosophy is a great way to understand the world, or at least understand your part of it. But beware, as soon as it is used to justify some BS or meaness towards other humans, you have to stop and get back in the human race.
Holy Wars are nothing more that Philosophy gone bad. Two groups of people trying to kill each other because they think their imaginary friend is best. Is that any way to live (or die)?
And lastly, this life is very beautiful. There are things that we simply cannot understand. Accept that, and enjoy the beauty. If you believe in an afterlife, then its good to assume that we will have a greater (but probably not total) understanding of life when we get there. If you don't believe in an afterlife, be calm and enjoy what time you have here and now.
Love someone today.