Good luck with the current work! If I can recommend, try saving up and investing into Clip Studio Paint Pro, it's the best SW to get right now at a reasonable price when it comes to art and its pretty cheap as well!

Ow, if you use it, I have a question: Does this program has a blending tool, to make smooth shadows and that lets me blend colors? I mean, that is the strong point that kepts me using Sai. Adobe, Corel, krita, manga studio, and others I don't remember doesn't have it.

It does! It actually has several in-built blending tools and you can even download your own. I think you should be able to import Sai tools too, but not sure about that.