As somebody who reads and speaks each of the languages in your illustration photo, I could probably chime in productively. (I used to be very good at writing Russian, but besides my native English, the only language I feel confident writing in today is French.)

Russian was "easy" for me in the sense that I went to a formal military immersion school for a year, spending more than 6 hours a day in class reading, writing, listening, and speaking. And then a good 2 hours minimum of homework at night, often more.

So that doesn't really count. If I didn't want to fail out, and I desperately did not, I had to do the work. Very few of us get that kind of "advantage" as language learners. Who has that kind of time?

French was very different for me, even though I lived in Montreal when I started learning. People think that means I had to speak French all the time. But that wasn't the case at all. Most of Quebec is not thoroughly bilingual, but most of Montreal is. I know plenty of anglophones in Montreal who never speak French. My francophone neighbors were so kind trying to accommodate me that I often had to plead with them nicely to actually speak French to me.

Those interactions certainly helped my ear. But the real learning came from a dedicated effort I made for 3 years to read novels in French and keep a vocabulary notebook — 2 hours a day, everyday except Sunday, no exceptions. During the final year, I supplemented that by watching French films for part of that 2 hours or for all of that 2 hours. Still keeping the vocabulary notebook. After 3 years, my French was better (I think) than my Russian was after a year of total immersion.

I was able to easily converse with any French person about any topic, so long as not too much slang was used. I was able to easily watch films and TV shows without subtitles. Was I native fluent? Of course not. But I was certainly comfortable, and I didn't even approach the 10,000 hour mark. I hardly ever practice anymore, but I can still read almost as fast in French as I can in English, meaning pretty fast.

Sadly, I've let my Russian and German fade, though I can still read fairly comfortably if quite slowly in both languages. When the Ukraine War started, I took an interest in what was going on and started watching Ukrainian-language television programs subtitled in Russian. It didn't take me long to start learning a little Ukrainian, and I almost decided to study it. It's sort of got my passion for languages going again. (Ukrainian is different enough from Russian to be a significantly different experience. Maybe about the degree of difference as between Italian and Spanish? Maybe a bit closer than that. But understanding Russian does not equal understanding Ukrainian, just having a head start.)

But the language I really think I need to start studying for real is Spanish. I'm constantly annoyed that I can almost but not quite read Spanish. I want to put the same methodology I used with French into Spanish. After all, I live in the United States where you can find Spanish speakers just about anywhere.

Sounds like a good project for my 60s!