Some surahs start with words that interpreted as pretty generic but in context of this possibility may be indicative of the language. Also many surahs starts with isolated letters called: Muqattaʿat. Possible languages suggested: English/Latin, Chinese, Persian, Arabic… alongside with likely mainly a language similar to Turkish.
But this doesn't seem possible unless there is a complicated situation. Maybe there are frequent descriptions in the main languages in the parts with other languages. Because Quran is very repetitive the idea of some surahs being in entirely in various languages sounds very far fetched. But maybe some parts are like dictionary or there is a complicated situation. Regardless, there is a sitation with especially English and Latin. (I only know English and Turkish.) It seems like El-participle was read as “Re” in Latin. The similarity between English past tense suffix "-ed", English definite participle "the" and Turkish past tense "dı" extremely eye catching. End not just this. “De” also means “tell” in Turkish. “da/de” both used as conjuction similar to "and" and as a suffix that can mean “in”. This is really just impossible to be a coincidence. Although I didn't explained it enough for it to understandable why. At least for anybody. In worst case people manipulated English and Turkish to make it seem like this is the case. Actually without any doubt the “de/da” suffix in Turkish and other uses like in case where it means to tell cannot be explained without some level of misunderstanding when understanding Quran. Sole origination from Quran doesn't cut it. Clearly some grammatical elements in Quran which doesn't supposed to be pronounced or reflected in verbal language carried to spoken Turkish. This one is really crazy undeniable situation. But I can't really provide a systematic explanation for it. I may add some more examples later. With Turkish there are actually crazy artifacts. I should create a page for it because I almost forget how crazy the situation is I wasn't looking Quran recently and some things are almost totally out of my mind. There are artifacts in Turkish originating from the alphabet of Quran. One example was above but despite it is actually pretty crazy one I think it is not that much more crazier than some other situations.
I also think that the parts considered Arabic are non-phonetic and follow a semantic structure, where words are connected using different operators and understood based on meaning rather than pronunciation. Pronounciation of Quran depends on dots and diaritrics marks added later. So this is actually very good explanation for undeniable situation.
It is also possible that common concepts are prefixed with El-Participle.
The idea of multilingual book sounds far fetched for various reasons but in any case Quran is likely not a straightforward reading book. Most likely there are frequent descriptions and definitions about concepts.