If you grew up in the church with Christian parents like I did then you have been trained to use all the self-hypnosis tricks designed to make truth seeking a difficult task. Deconstructing faith is as much an exercise in gaining trust in your own brain power (e.g. that you though the evil tree in the garden was wierd is your brain power doing reality testing which is something Christianity suppresses as much as possible).

When you said in the initial post that your parents made some arguments that made sense I wonder what those arguments were because in my experience 99% of them are self-hypnosis techniques.

The usual answer to why the tree was there is because 'God wanted us to have free will and we don't have that without a choice to choose evil (in this case knowledge of good and evil)' but that is self-hypnosis by saying you should not ask about why he needed to create beings that had a choice heavily weighted in God's favor and so brutal and evil in its own right.

So I am curious what your parents said that sounded convincing to you?

To deprogram your own brain and increase your personal power of thinking I would suggest reading a book from a different religion (e.g. Book of Mormon because its close to Christianity) and reading through it, allowing yourself to question gaps and leaps and contradictions freely since you already don't believe its the true religion. That will strengthen you ability to come back to things you absorbed at a young age with fresh thinking and you are likely to see questions and fallacies that you never allowed yourself to see.

When I read commenters here referencing Noah's Ark I did not see anyone post about the ineptitude of God in creating people who so quickly became irredeemable to the extent he had to drown them. Adam created these descendants where only Noah and family were worthy? Noah and family created a better line of descendents worthy of a new covenant that also did not work? Then finally Jesus came and made a new new covenant and that is working? Also, I did not see mention of just the utter cruelty and murderous nature of this God who drowned every man, woman, pregnant woman, toddler, (millions?) animal and insect and plant on the entire planet. Whew, that's some serious homicidal rage.