No amount of exceptions and quirks will prevent you from learning any language as long as you have lots and lots of exposure. After your reach a certain base level you just keep improving as you use the language, and even the exceptions start to feel natural.

English is the only language other than my mother tongue I have achieved this level with. I'd like to think at least in writing it's indistinguishable from a native speaker. Theoretically tho German should be easier for me as I'm Dutch. But my German never reached the same level because of the difference in exposure

What I think is interesting about the word flea market is that it's a calque in pretty much all languages.

The Swedish word is "loppis", which is a cutesy colloquial term for "loppmarknad." Loppa, meaning flea, and marknad meaning market.
Flohmarkt in German also means lit. "flea market."
Marche aux puces is French, where "puce" means flea, I think this might be the origin of the term.
Japanese has the casual term フリマ (fleama), short for フリーマーケット, which is just the English term "flea market", there's also the term 蚤の市, just meaning "market of fleas."

I believe Portuguese calls it a "thieves' market", but Spanish, Italian, Russian, Turkish, Dutch, and Mandarin all use their own native words for "flea market"; mercado de pulgas, mercato delle pulci, Блошиный рынок, Bit Pazarı, Vlooienmarkt, 跳蚤市场.

For all of the concepts and such that are identical across cultures, few things have universal names. Typically they enter the language as loanwords as well (e.g. karaoke, from Japanese '空オケ', hollow orchestra), so the term "flea market" stands out to me. I'm sure there are lots of other similar things I'm not aware of though.

Edit: It's worth mentioning that other than Swedish (native), English, and Japanese, I don't speak any of the other languages. I've asked a Russian-American friend about the Russian term, and a friend in Taiwan about the Mandarin term. Otherwise I've checked dictionaries and the like. Don't take my word as fact, I'm not a linguist. It was just a pattern I found interesting, because the term itself is so particular. Any and all corrections are more than welcome.

I'm also delighted by the discussion this has sparked! 💖

English is not a language.

English is 6 drunk raccoons driving an M1 Abrams through a Wendy's drivethru.

𝕯𝖎𝖊𝖘𝖊 𝕶𝖔𝖒𝖒𝖊𝖓𝖙𝖆𝖗𝖘𝖊𝖐𝖙𝖎𝖔𝖓 𝖎𝖘𝖙 𝖓𝖚𝖓 𝕰𝖎𝖌𝖊𝖓𝖙𝖚𝖒 𝖉𝖊𝖗 𝕭𝖚𝖓𝖉𝖊𝖘𝖗𝖊𝖕𝖚𝖇𝖑𝖎𝖐 𝕯𝖊𝖚𝖙𝖘𝖈𝖍𝖑𝖆𝖓𝖉

English is a germanic language. Is loanword an actual calque, and not an "evolved" version of a root word?

English is made by English speakers, and English speakers like to do a bit of trolling. Especially when it comes to speaking, reading and writing English.

When you learn a new language, you acquire its vocabulary. The etymology of the vocabulary is often irrelevant and can sometimes be beneficial. For example, when I started learning Spanish, I discovered that most French words ending in -al and -tion (a language I already know) are the same in Spanish. This means that I have instantly acquired hundreds of new words in my target language.

English is actually quite easy. Yes, there is a lot of vocabulary, but almost no conjugations or declinations make it easy compared to some others. My native has 19 different cases with 2-3 variants each for tonal coherence, and 2 modes of full verb conjugation (with additional exceptions of course).

That's a really interesting case of autological and heterological words

Every language has these. Chinese prefers calques to loanwords, but even it has 浪漫 lang4man4 romantic

Urgh, I resent the english language so much. It's so inconsistent and weird and unintuitive, which my dumb-dumb rules-focused brain just does not gel with. We should all just use Esperanto or something instead.

That’s true for every language, and maybe even more so. English is dominating the world, so the chance of inglish words and idioms getting to other languages is higher than from other languages to English.