“A reliable guide to Catholic doctrine is the Catechism of the Catholic Church (LINK). It is online and easily searchable.
A reliable guide to a personal relationship with Jesus Christ is the Bible. Any other doctrine whether by Angel or anyone else is from the pits of Hell.
Galatians 1:7-9 Douay-Rheims 1899 American Edition (DRA)
7 Which is not another, only there are some that trouble you, and would pervert the gospel of Christ.
8 But though we, or an angel from heaven, preach a gospel to you besides that which we have preached to you, let him be anathema.
9 As we said before, so now I say again: If any one preach to you a gospel, besides that which you have received, let him be anathema.
Looking at your CCC I find a prime example just how flawed your doctrine truly is. #841 Tells me that you and Muslims worship the same god. What have we learned so far is that you can’t leave Scripture because you end up dancing with the Devil and that will never end well.
That is not to say that what they believe about the One Creator is all true. Some of it is (for instance that the Creator is also the giver of moral law) and some of it isn't (for instance, they do not believe that God is Love.)
Like the Jews, they do not believe in the divinity of Christ, nor in the Incarnation, nor in the Trinity. Unlike the Jews, they believe explicitly and pointedly false things about Jesus Christ. For instance, the Koran says Jesus ("Isa ibn Maryam") was created in his virgin mother's womb, created like Adam, which makes him 100% creature, and neither son of God nor, really, son of Mary (since by the account of the Koran, she was not a real genetic mother, but rather something like a gestational unit or surrogate --- as if God would do such an insulting thing as surrogacy.)
Muhammad himself was rather an opposite to Christ, point-for-point on every point of their character. If you will kindly read to the end of the section, you will notice this conclusion on the non-Christian religions:
844 (LINK) In their religious behavior, however, men also display the limits and errors that disfigure the image of God in them:
Very often, deceived by the Evil One, men have become vain in their reasonings, and have exchanged the truth of God for a lie, and served the creature rather than the Creator. Or else, living and dying in this world without God, they are exposed to ultimate despair.
Those who portray the Catechism as being broadly pro-Islam haven't even read the section through.
I find a similar error in the idea that the Catechism is a rival to Scripture. It is not. It is based on Scripture. It would make as much sense to say that the Christmas carols we sing in church--- like "O Come All Ye Faithful" --- are rivals to or substitutes for Scripture, when in fact they are the same truths in different words.