An experiment with phonetic writing

[ololololo]

There's no comparison between a person who is conversational in the spoken language and intimately familiar with the writing system in question and naively trying to puzzle out an unrecognizable writing system in a language they cannot reliably understand.

You can speak French without knowing how to write it. Don’t try to dispute this; there are still completely unwritten languages in the world, and people somehow manage to communicate in them.
The only nuance is that you will write the language the way you hear it. And here, unfortunately, you can hear it in different ways: ujuvi, oudjouvi, oujove, oujudervey, etc.
I’m not a proponent of the Chinese theory (because it’s largely unprovable), but I can’t deny this fact.

Oh, on top of that, you might not speak French perfectly  There’s such a thing as an accent. If you don’t understand what I mean, watch some movies where Russians try to speak broken‑English.