Bible and Sages

Hello Rabbi Michi,
A question that has been on my mind for a long time. I'm not very familiar with the sources and I'll ask this in general terms:
When you study the words of the sages in the Gemara and the Midrashim, you learn about many laws, regulations, and values ​​that we are commanded to follow. In addition, there are countless narratives about Judaism – reward and punishment, hell and heaven, the wicked and the righteous, the future and angels, etc. Now, the sages of course try to reconcile their narrative with the Bible with endless commentaries and sayings that rewrite the biblical period and its characters so that they fit the above: King David was righteous, Samson was equal to Moses and Aaron, and so on and so forth. I don't have any more examples in mind, but you receive endless commentaries and explanations that paint a certain picture of Judaism and the Bible for you.
But then you go to study the Bible and you don't see anything that mentions any of this, not even in the slightest. There is no mention of conversion, of the prohibition of mixed marriages, and in certain periods – of idolatry, not to mention all the laws and commandments that were not observed. You encounter murder and prostitution on every second page. In short, it seems that there is simply almost no trace of the Judaism of the Sages trying to present and it seems that they simply do not correspond with each other.
I know I've mixed up a lot of topics here, but their common denominator is what's difficult for me: What is the meaning of this evolution that Judaism underwent under the hands of the sages? Is it anchored in the Bible? Is it even possible to rationally reconcile the sages and the Bible? Didn't the sages create something completely new?
If you have written articles on this topic, I would be happy if you could direct me to them. thanks