You belive that islam is the answer to all, cause it says so in the quaran.
Thats a very good point!
The answer to your question is simple, God created us:
He Who created Death and Life, that He may try which of you is best in deed: and He is the Exalted in Might, Oft-Forgiving;- [Qur'an 67:2]
He created this world for us, for our benefit. Where we would dwell for a temporary amount of time. This world would be a test to see if we would be obedient to the Creator, He would send us messengers from among ourselves with clear signs who would distinguish between right and wrong. I.e. what is good in the sight of Allaah, and what isn't liked in the sight of Allaah. They would warn us of the day when we will be raised back to life by the One who created us from nothing, and be questioned on our obedience and belief in Allaah and His Messengers'.
If you wonder why Allaah doesn't show Himself, - Allaah doesn't show Himself to us in this world, otherwise the concept of a test isn't really a test if the answers are given away is it?
Allaah has created many different forms of life; mankind, jinn, angels, and there are also other forms of life which we do not know of, yet they are a creation of Allaah. If you believe in a Creator, then it's easy to believe that He has power over all things, and He can create things which we do not know of and things which we do know.
The Qur'an is the truth because it is the revelation of Allaah revealed to His final Messenger, peace be upon him. The Criterion between good and evil, truth and falsehood, falsehood is the way of satan, and surely falsehood is weak, and without a doubt it will perish when Allaah wills. On that day the truthful will be rewarded for the good they did to please Allaah, whereas those who rejected their Creator, His Message and His signs - they will be the losers, and they will wish they could return back to this world to submit to Allaah. But by then it will be too late.
Allah is the Creator of all things, and He is the Wakil (Trustee, Disposer of affairs, Guardian, etc.) over all things.
To Him belong the keys of the heavens and the earth. And those who disbelieve in the Ayat (proofs, evidences, verses, signs, revelations, etc.) of Allah, such are they who will be the losers.
Say, [O Muhammad], "Is it other than Allah that you order me to worship, O ignorant ones?"
And indeed it has been revealed to you (O Muhammad SAW), as it was to those (Allah's Messengers) before you: "If you join others in worship with Allah, (then) surely (all) your deeds will be in vain, and you will certainly be among the losers."
Nay! But worship Allah (Alone and none else), and be among the grateful.
They made not a just estimate of Allah such as is due to Him. And on the Day of Resurrection the whole of the earth will be grasped by His Hand and the heavens will be rolled up in His Right Hand. Glorified is He, and High is He above all that they associate as partners with Him!
And the Trumpet will be blown, and all who are in the heavens and all who are on the earth will swoon away, except him whom Allah will. Then it will blown a second time and behold, they will be standing, looking on (waiting).
And the earth will shine with the light of its Lord (Allah, when He will come to judge among men) and the Book will be placed (open) and the Prophets and the witnesses will be brought forward, and it will be judged between them with truth, and they will not be wronged.
And each person will be paid in full of what he did; and He is Best Aware of what they do.
And those who disbelieved will be driven to Hell in groups, till, when they reach it, the gates thereof will be opened (suddenly like a prison at the arrival of the prisoners). And its keepers will say, "Did not the Messengers come to you from yourselves, reciting to you the Verses of your Lord, and warning you of the Meeting of this Day of yours?" They will say: "Yes, but the Word of torment has been justified against the disbelievers!"
It will be said (to them): "Enter you the gates of Hell, to abide therein. And (indeed) what an evil abode of the arrogant!"
And those who kept their duty to their Lord will be led to Paradise in groups, till, when they reach it, and its gates will be opened (before their arrival for their reception) and its keepers will say: Salamun 'Alaikum (peace be upon you)! You have done well, so enter here to abide therein."
And they will say: "All the praises and thanks be to Allah Who has fulfilled His Promise to us and has made us inherit (this) land. We can dwell in Paradise where we will; how excellent a reward for the (pious good) workers!"
And you will see the angels surrounding the Throne (of Allah) from all round, glorifying the praises of their Lord (Allah). And they (all the creatures) will be judged with truth, and it will be said. All the praises and thanks be to Allah, the Lord of the 'Alamin (mankind, jinns and all that exists).
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Qur'an Al Zumar - The Troops] (39: 62-75)