John 3:16 is a believing that is more than a mental conviction.  It is a belief (full trust) on which you stake your whole life.  The NT word “believe in Christ” has been oversimplified.  In the NT it carries the idea of “believe into.”  Try reading it that way for new insights.  This is what Jesus is saying.  “Believe into” means that we have come to the place that our life is in total solidarity with Christ.  That is where our salvation is found.  Paul came to that place when He said, “I am crucified “with Christ” (Galatians 2:20).  Those who are “in Christ” walk in the Spirit and not in the flesh (Romans 8:1-20).  In Christ we are a new creation (2 Corinthians 5:17).  In Christ is the blessing of Abraham (Galatians 3:14).  Keep believing into Jesus and see how it will bring you to a deeper relationship with Him.