According to Wikipedia, the original expression of course was: “parler franu00e7ais comme un basque quora”.

Is this expression true in English?

That is not correct if it’s a proverb. Why are proverbs not grammatical?

What is a similar expression which refers to non-native speakers if they don’t speak the language well, or have a very pronounced accent?

I’m not aware about direct proverb counterpart in English, so I would suggest translating it by its meaning :

“to speak broken English” — incorrect or awkwardly structured English, usually spoken or written by non-native speakers, usually ( Urban Dictionary

) TL;DR: The problem with translating proverb is need to convey the context. Historically, people were only aware about neighboring nations, and there were so many jokes about each other. Spanish cows and Basques: What is wrong with them? How can we avoid them for a second? Why’s it not sufficient to comprehend little details of a humorous context: what, if anything you’ve changed the context?

Can’t replaces Can’t in all

situations? There are exceptions. In wh-movement, the contraction should not be expanded unless you also change the word order. Why

can’t I have bacon? Why
shouldn’t I have bacon? Why can’t I
have bacon? //OK again, although formal

Stylistically, the choice between can’t and cannot is more complex. Generally, people use can’t in speech and informal writing, and can’t or can not in formal writing or very formal speech. Also, can might be used when you need to carefully distinguish it from can’t in speech.

What is the best way to describe my personal experience!