The absolute best thing I ever did in regards to figuring out bike maintenance was to buy a really crappy bike and just try to fix it, similar to what you’ve done. I went into it with the attitude of “if I break stuff, that’s fine, it was super cheap and old anyways” and wasn’t imagining I’d actually get a sound bike out of it. I used park tool YouTube videos mostly, and from that bike (and a few others) I learned how to do pretty much everything maintenance-related short of redoing the seals in a mountain bike fork (and that’s likely coming up soon). Wheel truing is tough but absolutely doable - again, but a really cheap bike (marketplace special), take the wheels off and apart, and just try to get them back together - that’ll force you to true them. Park tool again was an awesome resource for that.
For sure! I’m not always the best at responding immediately, but if you’ve got any other questions, feel free to chat me.