I have noticed that former Catholics are generally misinformed about what the Church teaches. It is well known in Catholic circles that there is a “crisis in catechesis,” and it has been going on for a long time. This means that many Catholics are not being taught about the faith. It is a tragedy, but it means that you can’t learn about what the Church actually teaches from former Catholics. I say this because it is only a matter of time before you encounter some.
If you want to learn what the Church teaches, a great way to do it is with the Catechism of the Catholic Church. Here is a PDF version. This version makes it easy to search for any word, such as salvation, justification, baptism, worship, Jesus, Mary, marriage, or anything else that interests you. This is what I did when I responded to the Catholic who was seriously considering leaving the Church for erroneous reasons surrounding marriage and virginity:
Reading the Bible is great too, but I think there is a temptation to view the Bible as if it just magically came to us intact. But Bibles don’t grow on trees–they did not just arise, intact and ready to use. None of us wrote it, translated it, or codified it. In one sense it is not ours. It belongs to somebody else on loan to us. There is an important history about how the Bible came into being, and that history means that we do not have the right to interpret it for ourselves.