language neutral nodes and primary menu (again, i know)

i have been trying and error all night and i really need some help.
- i use language neutral panel nodes on my site which have multilanguage content within them (this works fine)
- i have other content types in multilanguage
- both have menu items and i only want ONE menu item per translation bundle, and clearly ONE menu item for each language neutral panel node. i don't want to create multiple primary menus.
BUT
whatever i try (content selection, menu translation, menu translation node...) i can't get the primary links to show the correct menu items when switching to another language.
being on a language neutral node it only shows the language neutral items though the URL clearly states "en/pathtonode"

PLEASE SOMEBODY HELP ME - i am in dispair. can someone give me a quick step-by-step tutorial to get this working?