I wonder if there is only one programming language for all domains ,Should our lives, as programmers, been easier or difficult ?!

both, it is easier to integrate programs but nobody could learn the entire language since it would likely become immense very fast. there is a language like this already. its called Binary

I would say harder. Different programming languages have different applications. For instance, I wouldn't go and write a webpage in Fortran 90 or write a high-end application in TCL. But they both have their appropriate uses in different places, and I think that trying to incorporate everything into one big language would be a mistake.