How certain are we of what neurons and other building blocks of the brain actually do?

Every advanced tech has been used as a metaphor for how the mind works. People used to think the brain worked like a piston engine. Now people think the brain is like a computer. Some people also think we are a network ala the internet of biological persons. Lots of artists think in images. Some people see the brain as an evolving story. The people who have any idea how the brain works are those that have been studying it for decades, I would be interested in those metaphors.

No, because you’re being reductive. Biological organisms are clearly not like silicon computers.

Maybe biologist come up with the next big break through. I mean, if you want to match an organically grown organism ...

Is it clear that they're not alike? In the end it's all information and data being processed, whether by silicon or neural cell. What difference does the medium make to the end result?

Then at the very least, you should be able to simulate a biological brain, neuron by neuron, and get an intelligent computer that way. If you agree that's possible, you also have to consider whether it's the most efficient approach -- plausibly special algorithms could be invented that get the same intelligence at a fraction of the computing power.