I don't know if it's before or simultaneous, but I don't see how you can believe first, and then the Lord regenerates you.
Because scripture in numerous places says it happens after you believe then you become born again.
Notice what comes first in scripture - the order of how one becomes saved.
1- Repent , turn away from sin
2- the after you repent you get a new heart/spirit ,regeneration, new life, born again etc....
3- repent then you live, have life- ie new heart, spirit.
John below the same order in in his opening of the gospel and in his purpose statement for writing his gospel.
John 1:12-13
“Yet to all who did receive him, to those who believed in his name, he gave the right to become children of God— children born not of natural descent, nor of human decision or a husband’s will, but born of God.
Same order as above receive, believe, call on Him then the new birth follows.
John 20:31
“But these are written that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name.
Once again the order is consistent with the OT- belief/repentance precedes life.
Romans 10:8-13
But what does it say? “The word is near you; it is in your mouth and in your heart,” that is, the message concerning faith that we proclaim: 9 If you declare with your mouth, “Jesus is Lord,” and believe in your heart that God raised him from the dead, you will be saved. 10 For it is with your heart that you believe and are justified, and it is with your mouth that you profess your faith and are saved. 11 As Scripture says, “Anyone who believes in him will never be put to shame.” 12 For there is no difference between Jew and Gentile—the same Lord is Lord of all and richly blesses all who call on him, 13 for, “Everyone who calls on the name of the Lord will be saved.”
Again above we see its hearing the gospel, believing the message , confessing then calling upon the Lord results in salvation.
Acts tells us the same order in 11:18- "So then, God has granted even the Gentiles repentance unto life.” Repent precedes life.
Paul confirms the order in Ephesians below as well. Hearing and believing precedes the Holy Spirit that we were sealed with not before belief.
Ephesians 1:13
“And you also were included in Christ when you heard the message of truth, the gospel of your salvation. When you believed, you were marked in him with a seal, the promised Holy Spirit
conclusion: as we read in these SALVIFIC passages there is a consistent order.
1- hearing the word, the gospel
2- believing the gospel
3- receiving the gospel
4- calling upon the Lord
5- confessing Jesus is Lord
6- resulting in the new birth, born of God, salvation, eternal life, regeneration, born again
hope this helps !!!