Yeah, you can definitely understand computers to the point that nothing about them is really mysterious. It takes a while, but lots of people have done it. There might be lots that you aren't aware of - but none of it will come as a surprise once you've learned how it all works.

I guess at some fundamental level, though, it's based on (quantum) physics, and lots of that is still mysterious to us. But that's way deeper than anything you come across with computers.