Hi I have put language to italian in my editor , and all text and stuff is loaded in italian but how do I do if I want to save a plugin for italian and english and avoid localization problems?

I think you can't ...
The creation kit doesn't seem to support localised esp files. When you press the save button, all your strings are saved in an internal formal, you loose all your references to a string externalised file.
Then I think you'll need some 3rd party tools to create multilingual esp files.