Is bible is really true? YES... but you have to understand what the Bible is for.
The Bible was written to spread God's word, specifically the good news of the Gospel. In the Bible God teaches us who we are, how to live, and how we can be saved and get to Heaven.
The bit about how the world was made really isn't one of the important parts at all.
Now, if God had wanted to he COULD have said something like this
"In the Begining there was a singularity, and God said "Let there be Light" and and the singularity began to expand, and God saw that it was good, and approximately 10 to the neative 35th power seconds into the expansion, a phase transition caused a cosmic inflation, during which the universe grew exponentially, and God saw that it was good. And after inflation stopped, the universe consisted of a quark-gluon plasma, as well as all other elementary particles.Temperatures were so high that the random motions of particles were at relativistic speeds, and particle-antiparticle pairs of all kinds were being continuously created and destroyed in collisions. At some point an unknown reaction called baryogenesis violated the conservation of baryon number, leading to a very small excess of quarks and leptons over antiquarks and anti-leptons—of the order of 1 part in 30 million. This resulted in the predominance of matter over antimatter in the present universe, and God saw that it was good."
Of course the response of Moses and the Israelites would have been "WHAT THE HECK ARE YOU TALKING ABOUT????" and that talk about anti-Leptons would have gotten in the way of what God was trying to accomplish ...(which was to get across things like "Thou shalt not kill", "thou shalt not commit adultery"... Jesus's message of salvation).
So the Bible is TRUE but it is NOT a physics text, neither is it an anthropology text, nor is it an evolutionary biology text... for that matter it isn't a cookbook and it doesn't contain any cupons either.
Lots of good sincere people don't seem to understand that... they try to use the Bible in ways it was not intended... which is sort of like trying to get into the Super Bowl using last years tickets... yes they are real tickets... they are "True" in that sense... but getting into THIS years game is not what they are intended for.
why Evolution is believable? Yes... there is tons and tons of genetic and fossil and genetic data to show that it is true. I'm sure lots of people will detail it here better than I can.
Why do people are arguing with these 2 topics?
Because people do stupid things... its part of who we are.
When evolution first came out people who disliked the Bible in the first place (there are always people who dislike the Bible because it says things like "do not commit adultery" and they don't want to hear that) jumped on evolution as a way to attack Christianity.
There reasoning was that if the first part of Genesis wasn't totally scientifically correct then the entire book must be false from end to end. This of course does NOT follow logically. (Just because I find a typo in the Classified Ads of my Sunday Newspaper does not mean the whole thing is fake from end to end.)
Still that was their argument... it wasn't an honest argument, or even a logical one, but it was one they wanted to make because they disliked the Bible for other reasons.
Christians reacted in different ways. Some of them, like I said above, are good, sincere Christians that have a hard time with the concept of what "true" is. They don't like seeeing the Bible attacked and they can't get their heads around the idea that the first chapters of Genesis may just be an allegory for real events.
On both sides this is largely an emotional reaction, rather than a rational one. That is why it is so vicious and so few people are ever persuaded.