There is no text in the Bible, which clearly states that Yahushua existed before he was born. Such ideas have their origin in Gnosticism and other false religions. The idea that God or the gods could come down in the form of men was a common view in New Testament times.
And when the people saw what Paul had done, they lifted up their voices, saying in the speech of Lycaonia, The gods are come down to us in the likeness of men. And they called Barnabas, Jupiter; and Paul, Mercurius, because he was the chief speaker. (Acts 14:11-12)
Did apostles Barnabas and Paul agree with these ideas? No!
Which when the apostles, Barnabas and Paul, heard of, they rent their clothes, and ran in among the people, crying out, and saying, Sirs, why do ye these things? We also are men of like passions with you, and preach unto you that ye should turn from these vanities unto the living God, which made heaven, and earth, and the sea, and all things that are therein: (Acts 14:14-15)
Paul called such beliefs "vanities" and asked to "turn from these vanities unto the living God..." Bible states clearly, when and how Yahushua was born as the son of Yah and the son of man:
1) after Eve:
And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel. (Genesis 3:15)
2) After Abraham:
And in thy seed shall all the nations of the earth be blessed; because thou hast obeyed my voice. (Genesis 22:18)
Paul confirms that this is Christ:
Now to Abraham and his seed were the promises made. He saith not, and to seeds, as of many; but as of one, and to thy seed, which is Christ. (Galatians 3:16)
3) After Moses:
Yahuwah thy God will raise up unto thee a Prophet from the midst of thee, of thy brethren, like unto me; unto him ye shall hearken; (Deuteronomy 18:15)
Peter confirms that this is Christ:
Act 3:22 For Moses truly said unto the fathers, A prophet shall the Lord your God raise up unto you of your brethren, like unto me; him shall ye hear in all things whatsoever he shall say unto you.
...and here again:
This is that Moses, which said unto the children of Israel, A prophet shall the Lord your God raise up unto you of your brethren, like unto me; him shall ye hear. (Acts 7:37)
4) not an angel, but the seed of Abraham:
For verily he took not on him the nature of angels; but he took on him the seed of Abraham. (Hebrews 2:16)
5) After David:
And when thy days be fulfilled, and thou shalt sleep with thy fathers, I will set up thy seed after thee, which shall proceed out of thy bowels, and I will establish his kingdom. He shall build an house for my name, and I will stablish the throne of his kingdom for ever. I will be his father, and he shall be my son. (2 Samuel 7:12-14)
Is it about Yahushua? Yes, that is what the angel said to Mary:
He shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him the throne of his father David: And he shall reign over the house of Jacob for ever; and of his kingdom there shall be no end. (Luke 1:32-33)
6) New Testament is very clear about the birth of Yahushua:
The book of the generation of Yahushua Christ, the son of David, the son of Abraham. Abraham begat Isaac ... And Jacob begat Joseph the husband of Mary, of whom was born Yahushua, who is called Christ. (Matthew 1:1-16)
...and again:
So all the generations from Abraham to David are fourteen generations; and from David until the carrying away into Babylon are fourteen generations; and from the carrying away into Babylon unto Christ are fourteen generations. (Matthew 1:17)
7) Yahushua was born in Bethlehem in the days of Herod the king:
Now when Yahushua was born in Bethlehem of Judaea in the days of Herod the king, behold, there came wise men from the east to Jerusalem, saying, Where is he that is born King of the Jews? for we have seen his star in the east, and are come to worship him. (Matthew 2:1-2)
8) How was Yahushua born?
Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us. (Mat 1:23)
But while he thought on these things, behold, the angel of the Lord appeared unto him in a dream, saying, Joseph, thou son of David, fear not to take unto thee Mary thy wife: for that which is conceived in her is of the Holy Ghost. (Matthew 1:20)
Conclusion: Yahushua, the son of Yah, the son of man, had his beginning according the Bible in the time of Herod the king. He was not the only true God, the Father, he was the son of Yah. The pre-existence of Yahushua is false teaching coming to us from Gnosticism and pagan religions inspired by Satan. Modern Christianity is twisting Scriptures to defend their idea of "God the Son coming to earth, incarnated as a man, who lived and died as a man." This is not the true Gospel of Yahushua and his apostles.