The ONLY way you can BELIEVE that Jesus IS the Son of God and God in the flesh is through REVELATION from the Father (Matthew 61:17) through His Holy Spirit NO OTHER WAY!!! The Revelation can come in a dream, a vision, or just as a witness in your spirit however God chooses to reveal this TRUTH to you.
We can not prove to anyone that Jesus is the Son of YHWH (God) it will ONLY come through REVELATION. So if you are trying to get someone to believe that Jesus IS the Son of God and He IS also God in the flesh then pray and ask God to reveal it to them, ask Him to prepare their heart to receive it and give them ears to hear and eyes to see, His Holy Spirit will give them the Revelation.
When we get the Revelation and believe this with ALL our heart, we will not question it, doubt it, or try to understand it because our natural mind can not understand it but our spirit KNOWS it. When we live a spiritual minded life we don’t have a problems with it BUT when we are living a carnal minded life we will have problems holding on to our belief in this TRUTH.
“When Jesus came to the region of Caesarea Philippi, He asked His disciples, “Who do people say that the Son of Man is?” “Well,” they replied, “some say John the Baptist, some say Elijah, and others say Jeremiah or one of the other prophets.” Then he asked them, “Who do you say I am?” Simon Peter answered, “You are the Messiah, the Son of the living God.” Jesus replied, “You are blessed, Simon son of John, because my Father in heaven has revealed this to you. You did not learn this from any human being.”