How can I make work GetSimple in closed network ?

[mvlcek]

Maybe some change will be necessary, but wich one ?

I assume that the theme you are using, tries to load some resources (font file, javascript, etc.) from an external URL. Try to find these instances in the template files (e.g. "Innovation" uses Google font) and replace the links with links to local copies or remove them, if they are not really needed (like fonts).

Or use another theme that only uses local resources.