I don't know what action needs to be taken, but I'm pretty sure that something should be done.
Personally, I have little problems with the bilingual interface, although I would assume that it gets changed once the 'real' Lingala editors start getting to be the majority.
But, wouldn't it be better if it were monolingual, and people who need to use French can select that in their user preferences? Obviously, nobody at mi.wikipedia speaks better Maori than English, yet the interface is not bilingual there -- it's all Maori.
Also, the "uselang" can be added to the end of URLs and the interface will appear in that language.
However, the articles that are in English or French seem to me to not be the intention of a Lingala Wikipedia. There may be one or two exceptions (perhaps some pages about the language itself?), and one could put a page there that one intends to translate, but that latter should also not be more than 1 or 2 pages per editor.
I think the pages should be either removed, or replaced by stubs in Lingala, with perhaps a link to the English or French article for more information.
You mean interwiki liens? ;)
Mark