The Garden of Eden is real, according to the Catechism, as are our first parents. With a theistic evolutionist outlook, one can ascribe it and they to a special act of creation by God, a miracle of his intervention in the natural order. That’s the whole part of “theistic” in theistic evolution; if God can not guide, and intervene in, the process, it is nothing but atheistic Darwinism. Having the God in the Evolution allows for the guiding and intervention; without guiding or intervention, what is the use for God in evolution? The same for a progressive creationist, although progressive creationism lends itself more to it, as each and every kind was directly created by God.
The dogmata of the Church are these: the universe was created out of nothing. Adam and Eve were real people who committed a real, original sin, the stain of which we inherit. Each soul is created by an act of God at the moment of conception. Beyond these three propositions, there is much room for disagreement and debate amongst the faithful on questions of origins.
(That is, no, Catholics are not required to be theistic evolutionists, nor to be six-day creationists; these are but the two poles. All views that fit within those dogmata - essentially everything but atheistic Darwinism - is permissible to the faithful. At one pole, there is six-day creationism, at the other, theistic evolution. Between the poles, there is old-earth creationism, day-age creationism, gap theory, progressive creationism, intelligent design, etc.)
I like letting the text speak for itself, and avoiding the contortions necessary to make it fit with the wisdom of man (which is less than the folly of God…for God has made the wise foolish) which will be outdated in another century, much as phlogiston-fire was outdated in the 19th century but current in the 18th, so I’m a six-day creationist. (Also, that Darwinism was invented specifically to explain origins without the need for a creator sits unwell with me, although it explains not abiogenesis, or the origin of life from molecules.) The Bible is perfect; science is not; so when one seems to conflict with the other, the Bible wins. Note, that I say “seems”, as both science and the Bible, properly done and interpreted, can never conflict. But we won’t have a perfect science nor a perfect hermeneutic this side of the second coming. In science, there are many places for error; in the Bible, the only place for error is interpretation.
If you are interested in origins questions, I suggest reading
Darwin on Trial by Philip Johnson (I don’t know his theological position, and I suppose that’s a testimony to the unbiased nature of his work; his other works are also good),
Darwin’s Black Box and
The Edge of Evolution by Michael Behe (Theistic Evolutionist/Intelligent Design),
More than a Theory by Hugh Ross (Progressive Creationist), and
Genesis, Creation, and Early Man: An Orthodox Christian Vision (Six-Day Creationist) by Russian Orthodox Hieromonk Seraphim Rose. Sometimes one needs to break the chains of the mind first in order to see more fully other things; that’s why I recommend the books in that order; one can stop anywhere along the journey, or walk the road until the end.
I do not believe (although some of the above authors do, and give it the old college try, generally glossing “death” to mean “spiritual death”) that an old earth with “red in tooth and nail” evolution (i.e. not gap creation) and its death and pain before sin can be true; I believe only six-day creation gives an adequate response, although others disagree
I believe all who think deeply on the question of origins come to the view shared by myself and Fr Seraphim Rose, although experience vitiates my belief.
Catechism of the Catholic Church:
375 The Church, interpreting the symbolism of biblical language in an authentic way, in the light of the New Testament and Tradition, teaches that our first parents, Adam and Eve, were constituted in an original “state of holiness and justice”…
390 The account of the fall in Genesis 3 uses figurative language, but affirms a primeval event, a deed that took place at the beginning of the history of man. Revelation gives us the certainty of faith that the whole of human history is marked by the original fault freely committed by our first parents.
(Comment: this can be read as implying that the Garden of Eden is figurative, while Adam and Eve are real.)
399 Scripture portrays the tragic consequences of this first disobedience. Adam and Eve immediately lose the grace of original holiness. They become afraid of the God of whom they have conceived a distorted image - that of a God jealous of his prerogatives.
404 How did the sin of Adam become the sin of all his descendants? The whole human race is in Adam “as one body of one man”. By this “unity of the human race” all men are implicated in Adam’s sin, as all are implicated in Christ’s justice. Still, the transmission of original sin is a mystery that we cannot fully understand. But we do know by Revelation that Adam had received original holiness and justice not for himself alone, but for all human nature. By yielding to the tempter, Adam and Eve committed a personal sin, but this sin affected the human nature that they would then transmit in a fallen state. It is a sin which will be transmitted by propagation to all mankind, that is, by the transmission of a human nature deprived of original holiness and justice. And that is why original sin is called “sin” only in an analogical sense: it is a sin “contracted” and not “committed” - a state and not an act.
when people reject God’s existence because of something that doens’t make sense to them about His creation, that’s very unfortunate and it’s good to remember that humans don’t know everything and science has been wrong many times in the past, since it’s constantly - evolving - pun intended