Once one comes to belief in Yeshua as Messiah, one becomes a new creature, and an adopted member of the family of God, owned and governed by the Spirit of God who takes up residence in one's life---forever---so that when Yeshua calls for us, His betrothed Bride, she goes, no ifs, ands, or buts.
What does believing in Jesus mean? I believe there was a guy named Jesus...
Or does it mean believing everything about them. What they said, what they taught, how they lived.
They believing in Him means living like He did. Living like He taught us to live. Following His example
in the things that He did.