Philosophy for beginners and philosophy books online

Hello Rabbi,
A. Reading the wonderful book 'The First Matzoi' aroused in me a desire to understand a little about philosophy, which to me is almost like Turkish. Can the rabbi recommend how I can begin?
on. And another question, not necessarily for the Rabbi but for all surfers, is whether and where one can read basic books on modern philosophy online for free (Kant's Day, etc.)
C. And while I'm writing here, another small question: does the rabbi know anything about the teachings of Christopher Langan, one of the most brilliant people in the world, who, according to Wikipedia https://he.wikipedia.org/wiki/%D7%9B%D7%A8%D7%99%D7%A1%D7%98%D7%95%D7%A4%D7%A8_%D7%9C%D7%A0%D7%92%D7%9F , developed some theory to "prove the existence of God on a rational and mathematical basis."
Thank you for the wonderful books and all the articles.