In Fatima, Portugal; there were three children that the Blessed Virgin Mary appeared to. She told them many things, including but not only that World War II would happen, Russia would be converted, and the Holy Father (the pope) would have much to suffer. the quote for this is in part of one of the many visions of the Blessed Virgin. I will quote it to you now.
"You have seen hell, where the souls of poor sinners go. It is to save them that God wants to establish in the world devotion to my Immaculate Heart. If you do what I tell you, many souls will be saved, and there will be peace. This war will end, but if men do not refrain from offending God, another and more terrible war will begin during the pontificate of Pius XI. When you see a night that is lit by a strange and unknown light [this occurred on January 28, 1938], you will know it is the sign God gives you that He is about to punish the world with war and with hunger, and by the persecution of the Church and the Holy Father.
To prevent this, I shall come to the world to ask that Russia be consecrated to my Immaculate Heart, and I shall ask that on the First Saturday of every month Communions of reparation be made in atonement for the sins-of the world. If my wishes are fulfilled, Russia will be converted and there will be peace; if not, then Russia will spread her errors throughout the world, bringing new wars and persecution of the Church; the good will be martyred and the Holy Father will have much to suffer; certain nations will be annihilated. But in the end my Immaculate Heart will triumph. The Holy Father will consecrate Russia to me, and she will be converted, and the world will enjoy a period of peace. In Portugal the faith will always be preserved…"
A maricle that happened there is this…CLICK HERE
In regard to part two of your question of why to believe Christianity, esp. the Catholic faith, is because it is the Truth. There is no way I can convince you, esp. on the Web, but if you are open to God and ask Him to reveal himself to you, and have an honest desire to know who God is, then He will tell you. I hold nothing against my brethren in other religions, such as muslims, protestants, hindus, and and Jews, but they know only part of the Truth, not that we know the whole Truth, but we know the most. There is a wheel of religions, the center is the Truth/God, each religion is a different distance away from the center, and each is moving towards it. Others have access to fast food resturants, and 1-3 star resturants, but we have access to 4&5 star resturants, metaphorically speaking. But the Church will not be made perfect until the second coming. I hold a huge respect for many non-christian religions such as islam. But mine is the most correct, I know this from God, both from Him speaking to me in my heart and from visions others have recieved that He has told me are true. But again you must ask Him to reveal Himself to you if you want to know the Truth. I cannot convince you by myself.