But didn’t saint Mary said in the Gospel of Luke 1:47 " and my spirit rejoices in God my Savior"
Why would she need “Savior” if she wasn’t born with the original sin ?
Here’s an analogy that the Church has used for centuries.
Say you have a man walking down a road, and in the middle of the road is a pit, and he slips and falls into it. Then another man comes and throws a rope down and pulls him out. The guy who fell into the pit has been saved.
Now you have a different man walking down that same road, but before he falls in, someone grabs him by the hand and says “Stop!” This guy then never actually falls into the pit, but he could still turn around to the person who grabbed his hand and say, “Oh THANK YOU! You saved me!!!” Even though nothing technically happened to him. He was saved preventatively, but nevertheless still saved.
Look guys, I wanna be Catholic too but I can’t believe that saint Mary was born without the original sin. especially that the idea of Mary born without sin come in the 1844 or something like that, so it is something new.
I’m glad you want to be Catholic! I hope we can help you with this roadblock.
First of all, it’s not actually a new teaching. It was believed from the very beginning. We have evidence of the Church fathers believing in this.
Here’s a few quotes from the fathers
Ephraim of Nisibis AD 350:
You alone and Your Mother
Are more beautiful than any others;
For there is no blemish in You
Nor * any stains * upon your Mother.
(Nisibene Hymns 27, no. 8)
Ambrose of Milan AD 388:
Come then, and search out Your sheep, not through Your servants or hired men, but do it Yourself. Lift me up bodily and in the flesh, which is fallen in Adam. Lift me not up from Sarah but from Mary, a virgin not only undefiled but a Virgin whom grace has made inviolate, free from EVERY stain of sin. (Commentary on Psalm 118, 22, 30)
Augustine of Hippo 415 AD:
Having excepted the Holy Virgin Mary, concerning whom, on account of our Lord, I wish to have absolutely no question when treating of sins,-for how do we know what abundance of grace for the total overcoming of sin was conferred upon her, who merited to conceive and bear Him in whom there was no sin? - So I say, with the exception of the Virgin, if we could have gathered together all those holy men and women and asked them whether they were without sin, what would we have supposed to have been their answer? Would they not have declared in a single voice: If we say we have no sin, we deceive ourselves. (Nature and Grace, chapter 36 and 42)
That quote from Augustine is very significant, since he was arguing in this work against Pelagius, a heretic who denied man had original sin and can work his way to heaven apart from God’s grace. Augustine’s whole argument is no, men are born in original sin and are all sinners, but he goes out of his way to exclude Mary from that statement.
So the Immaculate Conception was clearly believed in the early days of Christianity. I only quoted three, but there are literally dozens more of this same stuff from the fathers of the Church. A dogma being defined is not when it first appears, or is believed, but only when it is made infallible, so there remains no doubt about it.
The Immaculate Conception, and all the Marian Dogmas in fact, are really centered around Christ. It’s because of who HE is, that Mary is so blessed. Not anything she did of her own, and she would be the first to admit that to you.
Anyway, hope that helped a little. I got so much more to say about this, but this post is getting a little long

Let us know if you still need more help understanding anything!