Here are the relevant sections of the Catechism, perhaps reading the entire section for each of these with your friend would help.
Regarding the nature of God and Creation:
213 The revelation of the ineffable name “I AM WHO AM” contains then the truth that God alone IS. The Greek Septuagint translation of the Hebrew Scriptures, and following it the Church’s Tradition, understood the divine name in this sense: God is the fullness of Being and of every perfection, without origin and without end. All creatures receive all that they are and have from him; but he alone is his very being, and he is of himself everything that he is.
Errors concerning God:
285 Since the beginning the Christian faith has been challenged by responses to the question of origins that differ from its own. **Ancient religions and cultures produced many myths concerning origins. Some philosophers have said that everything is God, that the world is God, or that the development of the world is the development of God (Pantheism). Others have said that the world is a necessary emanation arising from God and returning to him. **Still others have affirmed the existence of two eternal principles, Good and Evil, Light and Darkness, locked, in permanent conflict (Dualism, Manichaeism). According to some of these conceptions, the world (at least the physical world) is evil, the product of a fall, and is thus to be rejected or left behind (Gnosticism). Some admit that the world was made by God, but as by a watch-maker who, once he has made a watch, abandons it to itself (Deism). Finally, others reject any transcendent origin for the world, but see it as merely the interplay of matter that has always existed (Materialism). All these attempts bear witness to the permanence and universality of the question of origins. This inquiry is distinctively human.
Creation ex nihilo:
296** We believe that God needs no pre-existent thing or any help in order to create, nor is creation any sort of necessary emanation from the divine substance.** God creates freely “out of nothing”:
If God had drawn the world from pre-existent matter, what would be so extraordinary in that? A human artisan makes from a given material whatever he wants, while God shows his power by starting from nothing to make all he wants.
297 Scripture bears witness to faith in creation “out of nothing” as a truth full of promise and hope.
Regarding the “pre-existence” of the soul:
366 The Church teaches that every spiritual soul is created immediately by God - it is not “produced” by the parents - and also that it is immortal: it does not perish when it separates from the body at death, and it will be reunited with the body at the final Resurrection.
**1013 Death is the end of man’s earthly pilgrimage, of the time of grace and mercy which God offers him so as to work out his earthly life in keeping with the divine plan, and to decide his ultimate destiny. When “the single course of our earthly life” is completed, we shall not return to other earthly lives: “It is appointed for men to die once.” There is no “reincarnation” after death. **
1022 **Each man receives his eternal retribution in his immortal soul at the very moment of his death, **in a particular judgment that refers his life to Christ: either entrance into the blessedness of heaven-through a purification or immediately–or immediate and everlasting damnation.