Explain to me why the Eastern Orthodox church is the true church.

Check the churches in the New Testament. They are in Turkey (the 7 churches of Asia, the churches of Galatia, the church of Antioch...), Greece (the church of Athens, the church of Thessaloniki...), Italy (the church of Rome), and Palestine (the church of Jerusalem). If we account only for those communities that kept historical continuity with those early churches (so, if we put aside those churches that exist in those places but were established much later, or that consciously converted from one tradition to another)... the church of Rome is historically Catholic, and every other church is historically Orthodox (mostly Eastern Orthodox, although a couple, like Antioch, can be reasonably claimed by the Oriental Orthodox too).

Unless one believes in a "great apostasy", it only makes sense to join a church that has direct material, historical, geographical, cultural... continuity with the very churches of the New Testament. Or, if one does not live in those areas, then at least to join a church that is in communion with those churches.

But of course, those churches themselves aren't in agreement anymore, even though they used to be: now some are Catholic, some are Eastern Orthodox, some are Oriental Orthodox. Well... I would personally certainly rather trust those who still read the New Testament in its original language. So, the Greek Orthodox. It's not just about correctly understanding the text, but it's about a whole framework and manner of seeing things that is inherited from the Jews who read the Septuagint, and the apostles who wrote the New Testament, and the communities who received them... This isn't to claim that those who use Latin or Coptic or Ge'ez or Syriac are necessarily wrong (indeed, not even the Eastern Orthodox use Greek alone), but other languages are far more at risk of drifting away from the traditional understanding of the scriptures, and I think we especially see that today among anglophone Protestants.

So, because it has the strongest material, historical, geographical, cultural and linguistic continuity with the original Church Jesus built, I trust for now the Eastern Orthodox Church. But I'm also favorable to the Oriental Orthodox as dialogue in recent times was very encouraging. And I wouldn't outright discard the Roman Catholics (who can claim continuity with the New Testament's church of Rome, which both Peter and Paul visited and to whom Paul wrote an epistle), the Assyrian Church of the East (indeed, the prophet Isaiah prophesied there would be an altar to God in Egypt and in Assyria), and even the Orthodox Jews (who inherit the Hebraic and Aramaic tradition of the Old Testament, while the Greek Orthodox inherit the Greek and the Syriac and Assyrian churches inherit the Aramaic). But I cannot understand why someone who has read the Bible would want to belong to any other community, that has no continuity with the Bible at all except that they claim they know better than those who have always been studying it in ancient languages and cultural/religious frameworks.

I highly recommend Becoming Orthodox by Peter Gillquist. It covers all of this. The Orthodox church follows the original biblical cannon (Protestant Bibles have several books deleted) and honestly that was the deal-cincher for me. That, and we have direct biblical evidence (think the original Jewish temple) that God is fine with icons. Jesus established the church with His apostles and disciples, for them to carry out and pass on. So what you would need to do is find out what they believed and practiced, and go from there. Protestant churches sometimes try to reach into apostolic practice, but it's shallow and inconsistent, as far as I've seen (spent 25 years in Protestantism) if they even try.

Before the year 1054 there was only one Christian Church in the world. It is/was an "apostolic" church, meaning it's teachings, traditions, and leadership were handed down by the apostles. After Christ's resurrection the apostles went to different areas to teach the way of Christ and establish his Church. Each major Christian center of the ancient world (eg, Jerusalem, Rome, Constantinople, Alexandria, Antioch) was a center where an apostle was preaching and establishing the Church. However, in the year 1054 the Bishop of Rome and the other four bishops had a break-up (the Great Schism). We Eastern Orthodox believe we are closest to the original Church (or, "most true") largely because we have changed the least since that break-up. After the Bishop of Rome became the Pope and established absolute authority over the Western church, then the Western church began to change faster; change in the Eastern Churches happened much much slower, because in order to change anything all the Bishops have to get together and agree to change something, whereas the Pope can simply declare doctrine and it is done.

Historically, the written evidence seems to support the Eastern Orthodox view, as early church writing from before the schism (like Saint Basil, or Saint John of Damascus) describes religious practices that are more reflected in the modern Eastern Orthodox Church than in any other Christian Church today's. The Catholic Church is still seen as "valid" (to borrow a Catholic phrase), and they are still considered an "apostolic" Church, but the schism is still on place and most of the factors hampering Reunion have to do with differences that happened in the Western (Catholic) church since the Schism happened.

This is a poor explanation and I am not the best person to talk about this, but it is how I currently understand it as it was described to me. I would recommend reading about the Church history further, however, as it is a truly fascinating (if heartbreaking) topic.

Come and see.

We believe that since Pentecost the Holy Spirit has dwelled in our church, in our saints and bishops through apostolic succession and purity in the faith. God sent his Holy Spirit into his disciples, so that the Church could perform the sacraments/mysteries, and develop the Church Tradition which includes the bible, the church fathers, the writings of the saints, the ecumenical councils etc. One reason supporting apostolic succession is the replacement of Judas Iscariot by St Paul. If the aim was just to write a bible then god would have done it himself, however he didn’t, his Church wrote it with his guidance. One example of ecumenical councils is the first council of Jerusalem which is mentioned in Acts of the Apostles which prescribes what laws of the OT we as Christians should follow. For us, belief in Jesus isn’t enough, you need to believe in him the way the Church practises as the Church was taught by Jesus himself. We wrote the Bible, We authenticated it, without the Church there is no justification for Holy Scripture beyond it being just some guy’s opinion/ experience.

If you were God would you just give a random guy a manual and not explain it or would you accompany it with the apostolic teaching and the structure that the Church provides?

The only real true church are human beings. Remember when Jesus told the lady at the well that there will be a time when people will worship him in spirit and in truth?

John 4:24 Acts 7 & 17 Say God does not dwell in buildings made with hands.