Heading structure lost changing language

I have Italian LO on win7 - “Haeding X” styles are called “Intestazione X”.
Working with lots of copy/paste from the web or other english documents, I ended up with both styles. Eventually, I can merge english styles to their equivalent italian styles with “find and replace”
BUT
the big problem is that I lost my document structure (in navigator, TOC creation etcetera).
i can esaily test that now It relies on the english one (just create english named styles).
How can I revert the navigator to refer to the italian names again? Shall I submit this as a bug?
Thank you

Reported as → Bug 62666 - FORMATTING: the header’s styles structure switched from italian styles to english".

Please check menu “Tools → Outline Numbering”,

and select the appropriate Paragraph Styles for each level.

(Level 1 · Heading 1 – Level 2 · Heading 2 – etc.)

tools_outline-numbering

UI language en-US

UI language it-IT

grat job, very clear, thnx