For myself, I was looking at brushing up on my French and maybe even learn Spanish (or an easy language). I just came across a page in regard to 'hardest' languages to learn, these are ranked. If you're interested in learning a language, you may want to review the difficulty that language may have for English speakers or those who have English as their first language. Good luck... Link: 25 Hardest Languages to Learn, Ranked | Far & Wide (farandwide.com)
I have lots of recommendations for French-language material. Here's one: https://www.learner.org/series/french-in-action/ The top ones on the list look roughly like the difficulty ranked by the US State Department. One day I hope to learn Arabic.
The hardest language to learn is based on your native language. If your native language is Cantonese, I don't think Mandarin is hard to learn. If your native language is English, then I don't think it is hard to learn Spanish.
Of course, you're absolutely correct. The article was based on English speaking as ones first language.
I tried Danish once. It didn't seem that hard. The pronunciation is a bit weird, but not that bad. As in English, a specific letter isn't always pronounced the same way. Unlike English, though, there was some regularity to it. As for the grammar, it's a Germanic language. It's not all that weird, compared to English. Vietnamese is way more difficult.
I have worked with a variety of non-English speaking persons, but the toughest of the bunch was an Arabic speaker followed by Russian. This was way before translation apps and I remember trying to communicate with an English-Arabic book and an English-Russian book. Finally threw in the towel and had to get a translator.
Arabic is tough! I had an intern while I was working downtown, DC. Brilliant young man. He was an incredible worker and colleague. He was a Georgetown student. His mother was a native Arabic speaker and his father was a Farsi speaker. Arabic and Farsi were his household languages. Yet he had a hard time passing intermediate Arabic at Georgetown. Russian is tough too. I had a Russian friend tell me - Charles, just STOP! Russian is just too hard for you.
Counterintuitively, I've seen language learners struggle with languages that are too superficially similar to their native language because they can't seem to keep them separate in their mind. Want to roll some eyes? Try speaking Jamaican Patois without bothering to study the grammar and phonology. "It's just English with some island slang... right???" Or try using ASL signs in English grammatical order "It's just English on your hands... right?" Some languages are deceptively easy. I'd recommend taking a look at Bahasa if you want to impress your friends with an Asian language that an English speaker can actually pronounce. Since it's spoken in a predominantly multilingual area of the world, there's a lot of wiggle room for second language users to not quite say things right and still avoid cock-eyed glances from strangers. Other languages are deceptively hard. Americans often think that Spanish is somewhat of a cousin language to English. Hmmm, kinda sorta but not really. Of course, there's lexical similarity through both cultural diffusion and the English appropriation of Latin vocabulary. Beyond that, however, the grammar is only partially similar to English and every sound in the language except for S is phonetically different from its English counterpart. *I'd even argue that the Spanish S is not quite the same as the English S, even though it's indistinguishable to the ear. If you don't quite tighten your mouth in a certain place in a certain way when you say your S's in Spanish, you are nearly guaranteed to not be able to properly pronounce the sound that follows the S. This is from my subjective experience, not something you'd ever see in a textbook.
It made it a lot easier to pick up some Kwéyòl by listening to the way Dominicans speak English. It also helped that other than the adjective following the noun, its grammar is basically like that of English, and that it has no word endings. (What it does have is a lot of idiomatic expressions.)