Is it normal that i talk to myself when nobody is around

I do this and I would imagine most people have at some point. Maybe varying lengths of time but at "some" point. I usually do it either in the form of self pep-talk for something I may be getting lazy to do or as a release to verbally smite someone's actions when they aren't close enough in the world to hear it. Its a nice release and lets me confirm my thoughts.

I talk to myself as well. But that's usually cause I imagine myself having a conversation with friends I know or I'm trying to think about some sort of belief in my head that I just have to say out loud in order to make sure that what I'm saying is coherent. But at work, no way, I don't want people to think I'm some kind of freak, even though I'm sure plenty of people do this.

People can do this, for example when writing or reading many do it without knowing, sometimes it can be a early signs of schizophrenia which is fairly common now as more people have it then you think however this is unlikely unless you have any other symptoms, you could easily look up, I'm sure you haven't though, I talk to myself in some ways but harder to explain mainly when concentrating! Hope I helped :)

Yes, by all accounts it's as normal as the day is wide.

at least you understand yourself

if you're talking about your work to yourself I think that's normal and can actually be more productive as you stimulate multiple parts in your brain by doing so