On how to learn philosophy
Confessions of a Philosopher by Bryan Magee is probably your best bet. He covers most of the great figures quite accurately in great, easy to grasp prose. I can't think of a better introduction.
His book on Schopenhauer is also very good and will help build more critical thinking skills.
Beyond that, there's a lot of stuff, it depends on what you like. Russell's
History of Western Philosophy, though uneven, is a great reference.
Once you see a topic click, you can read intro books, lectures or just begin to read the classics. I think it's important to note that you never really finished with Plato or Descartes or Wittgenstein, it's a lifelong thing. So don't pressure yourself in mastery of the subject. It comes with time and changing perspectives.
Shout out to T Clark for mentioning
The Metaphysical Foundations of Modern science by Burtt. Knowing a bit about the history of the time period helps A LOT. What may seem silly to us now, was perfectly reasonable for the time, given what they knew. That's also a good book for the early-modern period in philosophy, which contains the most important figures outside of Antient Greece. It's a great book too.