Where does sin come from?
God is perfect, but why couldn't He make us perfect just like He is? Where does sin come from?
There's an answer that I find helpful on this issue: because of reason X, which is true in the same way that 2 + 2 = 4 is true, only God can be 100% perfect. That is, only God can be a completely perfect being.
Therefore God cannot make any other being equal to Himself in perfection. So God can make beings that are 99% perfect, or 99.999...% perfect, but only God can be 100% perfect. This is a fundamental limit on the nature of reality and God's power, because only the creator, only God, can be completely perfect.
Of course, in reply, it might be said that a computer program can be made to perfectly calculate someone's tax returns, and what about a perfect circle existing? So some types of perfection can be made outside of God, mainly relating, I guess, to something achieving a defined purpose. But only God can be completely perfect in every way. So a perfect circle cannot be completely perfect like God can be completely perfect. I think this makes sense.
So Adam and Eve could be created 99.9999...% perfect, but not perfect like God is. And neither can we.
And from that tiny, tiny amount of imperfection, after maybe billions and billions of years (it doesn't say how long they were in the Garden), Adam and Eve experienced the 'Fall'. And we would have done so in the same position, because we have a tiny, necessary amount of imperfection as well. The Garden was a good situation but, ultimately, it can't work forever.
The only way around it is for God to insert Himself into reality as a created being, with our vulnerabilities, and overcome our 'necessary imperfection' - our ability to be tempted by evil - by being God as well as human.
The way it works for God as a created being is that, for instance, Jesus would never sin in any possible situation because He is God although He was tempted because He is human (Heb 4:15).
Then God-as-a-created being absorbed all the effects of our necessary imperfection - our sin - into Himself on the cross, as a result of which everyone can "be found in [Jesus], not having a righteousness of [their] own that comes from the law, but that which is through faith in Christ" (Phil 3:9).
That solves the problem created by our necessary imperfection, which is the way it always led to sin - it's not a problem if you have a goodness which is not your own, but which is Christ's.
Ultimately, God found a way to forever sidestep our necessary imperfection through the cross, in a way that wasn't available in the 'Eden setup', although the Eden setup was 'very good' (Gen 1:31).