Wow. Lots of great questions! I'll give it a shot.
It doesn’t sound like your school taught much about the Bible, so naturally there are holes. The Bible has the answers to these questions but you have to study to get it. (No different than the work you have to do to become a brain surgeon, rock star, or olympic athlete.) But I’m happy to “jump start” the process with a few simple answers. I can back them up with actual Scripture if it turns out you are really interested in God's opinion.
If God writes the bible then who maintains it?
God maintains it, the same way he wrote it. The content is written for all time so it doesn't need any updates. The chief work is that of keeping track of what the original said while false prophets and false teachers work hard to introduce corruptions. Despite their corrupting, we have countless scholars (including many unbelievers) using different methods of discovering what the original text said yet still converging on reference texts that are 100% doctrinally compatible across many scholarly translations. Some of us consider that to be miraculous. (See my two part series on this remarkable outcome, just published in the past week, for more details.)
Perhaps the best example is the discovery of the Dead Sea Scrolls in 1947. They had been buried in a cave for 2200 years and matched the modern Bible on your shelf almost perfectly. It's hard to argue that is not miraculous!
And why are we allowed to pick and choose what quotes we like from the bible and leave those that we don’t? Does that mean God chose the bible as a guideline more than a set of rules? And if it’s rules why are you using it as a guideline?
We are not allowed to pick and choose. But Christians are fallible humans. We do lots of things we aren’t supposed to do. Nevertheless, Jesus set us free from hundreds of detailed rules and boiled it all down to simply “Love God and Love others.” If we do that, we will automatically fulfill all the other laws.
When I die, then I’ll either be eaten by worms or judged at the pearly gates.
I’d say its either "eaten by worms" or “cast into the outer darkness where there is wailing or gnashing of teeth” or “live forever in an upgraded Version 2.0 body in a perfect world as a child of God”. You don’t want to get that one wrong.
Why should I feel shame for being born? I haven’t sinned yet, but I am guilty for a millennia of people before me and their mistakes? Doesn’t sound fair!
You are not guilty for a millennia of people. You are suffering the consequences of a test that one ancestor, Adam, failed to pass. As a result of Adam failing “Plan A” (obey one tiny little rule of God), we are switched onto “Plan B” where we have to earn what was once offered as a gift. But over 6000 years humans have proven we can’t earn it. So we are given “Plan C” – trust God to earn it and take our punishment for us. Doesn’t sound fair? Really?
Why does God write that homosexuality is an abomination?
Who can know the mind of God? What we do know is what He has said offends Him. Perhaps because it violates His intended design or perhaps He knows what is best for us and for the human race in general.
Why is it fine to work on a Sunday even although Leviticus strictly forbids it?
Again, Jesus set us free from hundreds of detailed rules and boiled it all down to simply “Love God and Love others.” If we do that, we will automatically fulfill all the other laws including the Sabbath. Loving God means setting aside some time to focus on Him and think higher thoughts than we can do when we are consumed with working. Some people still do this on a fixed day; others develop their relationship with God on another day or, gasp, every day! Jesus set us free to focus on the intent of God’s laws like grown-ups, rather than a laundry list of rules like we give to our own children.
If we look at it critically then we’ll know that nearly all miracles disappeared and stopped happening after major advancements in medicine and technology, namely the video camera.
Well, there are public and private miracles. Most Christians have experienced answered prayers that defy the laws of probability. But these miracles are left for us to recognize or not. Public miracles intended to act as signs are much more rare these days because the time for signs is over until the last days. God tends to use signs to establish the credibility of His prophets and then expects us to listen to them.
I’ve never talked with god in my life,
Perhaps you should start. Developing a personal relationship with Jesus is essential for your spiritual growth. If you stand off from God and never approach Him, how can you be surprised that you are not making Spiritual progress?
and he’s strangely silent on a good few Political wrongdoings in the global scene right now.
The past 6000 years of human history are a demonstration to all Creation that humans cannot govern themselves and need to turn back to God as their ruler. So God allows us to experience the natural consequences of rejecting Him (or living on the same planet with others who reject Him.)
The evil that you see in this world is Satan being allowed to give it his best shot. God doesn’t interfere (with some exceptions) because to do so would be to help Satan be a successful ruler and the purpose of this world is to demonstrate to all us rebels that Satan is not who we should be following.
There will come a day (soon) when God will not put up with this any more. But He intends to prove His point before that by allowing things to get much worse.
Oh, and truth in advertising, Jesus has made it clear in the Bible that Christians are going to suffer ever increasing persecution until He returns...and that it will be well worth it!
:o)