Yeah, there are definitely people with talent for this sort of thing too. I actually have a friend who has an incredible ear for pronunciation, so if you give her enough native people to listen to she can talk and sound like a native even when she doesn't fully understand the grammar behind it, and that's a skill I doubt I could ever pick up no matter what my education was like. For what it's worth though, surrounding yourself with native speakers of a language is a great way to learn it, as long as you are actually speaking with each other in their language, because it will give you constant practice and also constant examples of how the language is actually used rather than what the formal rules for it are.
Based off what I've gotten out of linguistics professors so far, the main issue with learning languages as you get older is that your range of distinct sounds starts becoming fixed as you get older, which makes it hard to catch pronounced sounds that aren't part of your native language(s) and to make them yourself. To give a halting analogy of it, it's a bit like having a blindspot in your range of colors where you can be told that there's something in-between say yellow and blue, but you'd see green and think it's either a shade of blue or a shade of yellow rather than a distinct color in its own right. Except, y'know, with sounds.
Chinese is a tough one for sure, both for its grammar and the writing system. It's one of those languages that are a huge uphill for me because intonation follows a very steady, regular rhythm in Finnish, so trying to wrap my head around intonation changing the entire meaning of the words you speak is kinda tricky for me. It looks like a really interesting language to learn though, so good luck with it.