I am currently learning Chinese and Russian. Very different languages with very different challenges, but because of that it helps me not burn out on one language by switching for a few days or weeks to the other whenever i get fatigued with one.

With Russian, learning the alphabet was the easiest part. It also has enough of a connection to other European languages that many words are not entirely new and i can connect them to words in other languages i already speak.

The grammar is definitely the most difficult of all the languages i've learned or tried to learn so far, just because there are so many cases. But even there i frequently find parallels and similarities in the forms and patterns with my native language.

Luckily pronunciation is also not too big of an issue for me, but i can imagine if you're not from that part of the world and you are used to completely different phonetics it can get tricky.

What you say about acquiring grammar naturally over time is something i have always relied on when learning languages. Just drilling rules and forms doesn't really stick for me, so i need to use and hear them used in context over and over again.

The next task i've set for myself is to start looking into forming a kind of mental map of the ways that various compound words connect with each other and how base words change meaning through added prefixes, because i found there is a lot of that in Russian.

As for Chinese, it's practically the diametrical opposite. Everything i find easy about Russian i find hard in Chinese and vice versa. The grammar is very easy if not trivial, but the pronunciation is trickier than Russian, and the listening comprehension is super difficult for me still because of the tones.

There are very few European loanwords, so most of the vocab is brand new. And where Russian has fairly long but mostly unique words that are not that difficult to memorize, Chinese has a lot of really short words and a ton of homophones, which means you are constantly having to add more meanings to sounds you already learned.

Also, as a beginner not really being able to hear tones well, that basically quadruples the amount of homophones for you, and you need to kind of look for context clues as to which word is being used.

Fortunately, in writing most of that ambiguity goes away (though not all, which has been an unpleasant surprise to discover...), but learning to read it is a permanently ongoing task, and you are always learning new characters.

There are tricks to easier memorizing of characters and how they are pronounced, but that's just mnemonics, in the end you still have to learn each one individually.

Still, i'd definitely say i have an easier and more fun time with Chinese than Russian, for now. I'm thinking of starting to write down what I've learned so far. Writing things down has always helped me memorize things better... that's how i would always learn my formulas for exams in uni.

If i can get either language to about the level that my three years of French in high school got me, i would be happy for now.