English is a mongrel language, borrowing from everywhere. So some expressions used in foreign languages are understood by native English speakers, but not many. Only a minority of Americans, for example maybe one out of four, speak a foreign language to any degree of fluency.

Your question reminds me of a story. I was talking to a German immigrant in California about my computer. I told her, "Yeah, my computer went kaput, so I need to take it to the shop to get repaired." She was surprised that I used the word "kaput" since it's originally from German, which I didn't know at the time. Well, there are many words in English that have origins in other languages, but we use them so often that we think of them as "English" words. And when I started studying French, my French teacher pointed out how many French words I already knew because we use them regularly in English, such as a common word like "encore."

It's a little more complex than that. A language will naturally adopt some words from a geographically-neighbouring language, so because England is close to France and Germany, and the speakers often interact, the occasional phrase will be adopted. Also, if it's fashionable to use expressions from the other language, then more phrases and words are likely to be taken up in English. Please don't assume this applies to "any native English speaker". It still depends on factors like location and exposure. I spot Spanish expressions more often in American English, and as Australia is fairly close to southeast/east Asia, we're more familiar with expressions from those languages.

Deja vu is very common in English and most natives use and understand it. "Echt", however, is very foreign to native speakers. I, myself, have never heard of it.

Things like "deja vu" are loanwords in english and the majority of people will understand them, though I've never heard "echt."