You have said you believe "in what has been revealed to us and what was revealed to Abraham, Isma'il, Isaac, Jacob, and the Tribes, and in (the Books) given to Moses, Jesus, and the prophets, from their Lord." This is an unequivocal affirmation of the authority and accuracy of the Bible, which is the starting point for understanding the truth about the one true God.
I am going to proceed with the hopeful assumption that you are indeed a sincere seeker of truth, and not just blindly and unquestioningly following a religion you received from your family, culture, or social contacts. There is no question that Islam has a powerful dramatic appeal, but the true measure of validity is whether there is a factual basis behind the articles of faith. Muslims are taught to never question whether Mohammad was a genuine prophet, but why? The entire validity of Islam stands or falls on the question of whether Mohammad was a valid prophet of God. If Muslims are so sure they are correct, why are they afraid to examine this question, and why do they threaten violence against those who do?
"When Abram was ninety-nine years old, The LORD (Yahweh) appeared to him and said, 'I am God Almighty ; walk before me and be blameless. I will confirm my covenant between me and you and will greatly increase your numbers.'" (Genesis 17:1-2 NIV)
God made an agreement, or covenant, with Abraham, that the nation which would emerge from his descendants would be the nation bringing the knowledge of God to the world. The earliest accounts of these encounters between God and Abraham are found in the Biblical book of Genesis starting with chapter 12.
"I will establish my covenant as an everlasting covenant between me and you and your descendants after you for the generations to come, to be your God and the God of your descendants after you. The whole land of Canaan, where you are now an alien, I will give as an everlasting possession to you and your descendants after you; and I will be their God." (Genesis 17:7-8 NIV)
As a confirmation to the childless Abraham, by now an old man, that God would accomplish this covenant, Abraham was promised a son born to his wife Sarah. This son would be the descendant from whom this new nation would arise.
This extraordinary miracle birth did take place, and God instructed Abraham to name the boy Isaac.
"'I will bless her and will surely give you a son by her (Sarah). I will bless her so that she will be the mother of nations; kings of peoples will come from her.' Abraham fell facedown; he laughed and said to himself, 'Will a son be born to a man a hundred years old? Will Sarah bear a child at the age of ninety?' And Abraham said to God, 'If only Ishmael might live under your blessing!' Then God said, "Yes, but your wife Sarah will bear you a son, and you will call him Isaac. I will establish my covenant with him as an everlasting covenant for his descendants after him.'" (Genesis 17:16-19 NIV)
So God clearly decreed that Isaac, not Ishmael, would be the bearer of the covenant promises.
As would be expected under the circumstances, a conflict developed between the boys, and between their mothers.
"Abraham was a hundred years old when his son Isaac was born to him. Sarah said, 'God has brought me laughter, and everyone who hears about this will laugh with me.' And she added, 'Who would have said to Abraham that Sarah would nurse children? Yet I have borne him a son in his old age.' The child grew and was weaned, and on the day Isaac was weaned Abraham held a great feast. But Sarah saw that the son whom Hagar the Egyptian had borne to Abraham was mocking, and she said to Abraham, 'Get rid of that slave woman and her son, for that slave woman's son will never share in the inheritance with my son Isaac.' The matter distressed Abraham greatly because it concerned his son. But God said to him, 'Do not be so distressed about the boy and your maidservant. Listen to whatever Sarah tells you, because it is through Isaac that your offspring will be reckoned. '" (Genesis 21:5-12 NIV)
Abraham was upset because Sarah wanted to expel Ishmael, but God told Abraham it was He who has made the decision to do that. Ishmael would not share in any of the covenant promises.
Though God Himself had said at the end of Bible that the Scriptures were complete and no more prophets would be speaking the oracles of God, it is some six hundred years after Jesus when Mohammad from Arabia belatedly claimed to be a prophet. This descendant of Ishmael claimed to have new revelations from God, revelations which seriously conflicted with the message of the former prophets. Even the name of God is changed by Mohammad - it is no longer Yahweh, the God of Israel, but a previously unknown deity with the name of Allah.
The name and identity of God is a crucial point. Mohammad also claimed, like Abraham had, to be the one to convey the knowledge of the one true God to the world. And Mohammad said this "god" is the same one as Abraham's God. But it is not. Abraham's God had a different name, attributes, values, and message than the invented "god" Allah. And for this and other reasons too numerous to cite here, Mohammad did not qualify as a true prophet of the God of Abraham.
The standard Islamic answer to these discrepancies is the charge that the Jews and Christians, the agents and bearers of the Scriptures, had somehow changed and distorted the true message from God. But the obvious question is this: when did this supposedly happen, and what is the evidence? In the foundational story of Isaac and Ishmael, the account recorded by Moses existed for many centuries before Mohammad, and the historical basis for it was not disputed for 2,600 years. In fact, there is no evidence that anyone at anytime before Mohammad claimed that it would be Ishmael, not Isaac, who would inherit the covenant promises granted by God to Abraham. This is true of all of the many starkly contradictory teachings of Mohammad - no evidence whatsoever exists that the earlier prophets had been given a pure message from God which was later distorted into the form it now stands in the Bible. There simply is no evidence for Islam's absurd assertion.
It is compassion and mercy, not militaristic conquest, which is the essence of God's redemptive message to mankind. The ultimate provision of the covenant God made with Abraham to bring blessings to all the world was through the promised Messiah. He was prophesied to be a descendant of Abraham, Isaac, Jacob, Judah, and David, and would appear the first time to give his life as a sacrifice of atonement for sins. It is He who would be the culmination of the Word of God communicated to all the world.
"The Word became a human being and lived here with us. We saw his true glory, the glory of the only Son of the Father. From him all the kindness and all the truth of God have come down to us.... No one has ever seen God. The only Son, who is truly God and is closest to the Father, has shown us what God is like." (John 1:14,18 CEV)
King David prophesied this 1000 years before Jesus came about David's descendant who would become the King of the Earth:
"The one enthroned in heaven says...'I have appointed my own king to rule in Jerusalem on my holy mountain, Zion.' Now I will tell you what the Lord has declared: He said to me, 'You are my Son. Today I have become your Father. If you ask me, I will give you the nations; all the people on earth will be yours. You will rule over them with an iron rod. You will break them into pieces like pottery." (Psalms 2:4,6-8 NCV)
The prophet Isaiah, 700 hundred years before Jesus was born, described the Messiah who would be a descendant of King David (whose father was Jesse of Bethlehem):
"A shoot will come up from the stump of Jesse; from his roots a Branch will bear fruit. The Spirit of the LORD will rest on him-- the Spirit of wisdom and of understanding, the Spirit of counsel and of power, the Spirit of knowledge and of the fear of the LORD-- and he will delight in the fear of the LORD. " (Isaiah 11:1-3 NIV)
That man from Galilee, Jesus of Nazareth, is the great light to illuminate God's final message to the world, and no more prophets are needed after him.
"In the future he will honor Galilee of the Gentiles, by the way of the sea, along the Jordan-- The people walking in darkness have seen a great light; on those living in the land of the shadow of death a light has dawned.... For to us a child is born, to us a son is given, and the government will be on his shoulders. And he will be called Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace. Of the increase of his government and peace there will be no end. He will reign on David's throne and over his kingdom, establishing and upholding it with justice and righteousness from that time on and forever. The zeal of the LORD Almighty will accomplish this." (Isaiah 9:1-2,6 NIV)
You may dispute these facts, and it matters not to me if you do, for the truth stands by itself. But it would be to your benefit if you set aside your religious zeal and reexamine the accuracy of what you have been taught. It may be that the true God, the God of Abraham, is giving you this one chance to discover Him in truth. The God of Abraham, Isaac, and Jacob is a God who wishes to have a personal relationship with all humans who have been made in His image. Sadly, mankind has invented many errant religions which do not lead people to God, but away from Him. You may be very fervent in your religion, but if a religion is based on fallacies, it is worse than useless.
His message is not confused and contradictory, The Father sent the Son to be the savior of the world, as all the prophets had foretold. Believing in the authority of the Son is the only way to know the true God and have eternal life. As Jesus said,
""I tell you the truth, whoever hears my word and believes him who sent me has eternal life and will not be condemned; he has crossed over from death to life. I tell you the truth, a time is coming and has now come when the dead will hear the voice of the Son of God and those who hear will live. For as the Father has life in himself, so he has granted the Son to have life in himself." (John 5:24-26 NIV)