Actually I'm new to the mining, so I don't know how to do the maths

But anyhow I would be glad if someone could tell me how to calculate it

But I understand that this machine will not be that profitable
If you are new to mining, the big question is, how much do you pay for electricity?

To be honest, that is really only a question you ask yourself if you already have a bunch of hardware. Unless you can get a screaming deal on a GPU or something, I think you would be hard pressed to find anything for sale that will pay itself off in under 6 months, even with free electricity.