Can a big iOS update break your phone?

Hello, I have an iPhone 8 with iOS 12.

I can only update to iOS 16, and only with a computer. Surely it would have worked without it if I'd installed the updates properly, but oh well, that's just how it is now.

Anyway, I only have a Windows laptop, but theoretically it should work there too.

My only fear is that something will go wrong during the process and the phone won't turn on anymore…

Especially since it would be a switch from iOS 12 to 16? Could anything go wrong, or is there anything special I need to pay attention to to ensure a smooth transition?

Do you perhaps know how long such a process takes?

Unfortunately, I don't have the money to buy a new phone in the future, so I'm a bit worried, but also worried about possible data loss or something.

But I'm actually still very happy with my phone, the only annoying thing is that with iOS 12 a lot of things don't work anymore, both apps and certain websites in the browser.