What makes your faith true?

[Fake Messiah]

I'm not aware of contradictory bits or those which have been disproven scientifically.  For example, I don't hold to a literal 6 day creation view.  The Bible is filled with multiple kinds of literature written from various perspectives, both gentile and Jew, which have to be taken into account.  Most of the time, when I run into apparent contradictions or asserted scientific disproofs, I'm usually looking at misapprehensions on the part of the objector or worse, outright straw men that the objector knows to be false characterizations of the Christian point of view or my point of view.  So I really would have to ask for some kind of clarification as to what you mean, specifically?

Well you've got the bits where the prophets and Yeshua tell you the way of Moshe is the way of god and you must follow all the rules, and then you've got the bits where Saul and the other Greek speakers tell you the way of Moshe is no longer the way of god, and no rules need be followed. That's a pretty big contradiction, as you cannot follow both teachings.

Sure, in NT you have Jesus say "Do not think that I have come to abolish the Law or the Prophets" but he himself was sometimes a hypocrite in this, because he didn't follow all the rules from OT and spited them, like he refused to wash his hands before eating; he stopped a mob from stoning an adulteress woman.

So what is for good christian to do since Jesus never spells out which parts of the OT should be kept and which ones should be abandoned?
What Christians usually do is if the OT says stuff you like but that is not mentioned by Jesus (i.e. that homosexuality is a sin, etc.), then you'll firmly argue that it's clearly an important part of Christian theology since it's found in the OT. If, on the other hand, it says something you don't like, then you can just go ahead and ignore it since real Christianity is about New Testament anyway. The beauty of this game is that you can make the Bible say pretty much anything you want it to say.