Sidebar translations are approximative

[jum-s]

So far, when chosing my language as French, sidebar looks like:

Somehow "Translate" is "Traduire" but "Communication Channels" is not "Canaux de communication" (despite Communicantion_channel/fr existing)

Official documentation does not give many details on the question "The string, which will replace the item named "mainpage", is taken from MediaWiki:Mainpage. To set/change this text for users, who display your wiki in German, you can put the according text on the page MediaWiki:Mainpage/de."