What is the use of those in the game ? Since now I assumed they didn’t have to be translated like %s and %d but it is really tue ?
Yep, that’s correct, you don’t have to translate those parts.
The named <> tags are stripped out by the game, so they won’t show up when playing.
I think they’re partially to make sure the same string in different contexts remains unique, and partially to show what the words are being used for when it’s ambiguous.
Gettext does appear to have a solution for making strings unique, so i’ll be looking at getting rid of some of the tags after the next stable release, but for now you can just leave the bit inside the <> untranslated.
Does the same goes for the [] items ?
And thank you for the last answer 
I think the ones in [] should all be translated. Although some of them refer to keybindings, for example “auto[p]ickup”. For those if the letter isn’t in the translated word, you can just change it to indicate the letter however you want, “autopickup [p]” or something like that.
That’s what I did for the keybindings, but since now I encoutered two strings [vehicles] and [indoor] with wich i don’t now what to do…
Ahh, yep, translate those. It’s for the map editor, tells you about the currently selected tile (whether it has a vehicle in it, whether it’s indoors, whether it has a roof).
ok, thanks you