Is Jesus God?
In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. - John 1:1-2
And the Word became flesh and dwelt among us, and we beheld His glory, the glory as of the only begotten of the Father, full of grace and truth. - John 1:14
From the second verse it is clear that the Word is the One who was made flesh and dwelt among us. This is unmistakably talking about the Lord Jesus. It also becomes more evident as one read John 1 that this Word is the Lord Jesus Christ. The first verse we quoted above teaches us three things about Him. First, He was in the beginning. He Himself never did have a beginning. In what we might call the beginningless beginning, He already was. The second thing is that He was with God, that is, He was a distinct Person, living with God the Father. Then thirdly, we read that the Word was God. This puts the absolute deity of Christ beyond reasonable question.
Want another proof? In Exodus 3, Moses is asked to go and rescue the Israelites out of Egypt and he asks God what will he tell Israelites if they ask "What is God's name?". God responds to Moses in verse 14 "I AM WHO I AM". This is a name that signifies that God is always present. Only God can use the name "I AM" because He does not have a beginning nor an end unlike any man or animal or angels who all have a definite beginning. So, when we read John 8:58 - "Jesus said to them, "Most assuredly, I say to you, before Abraham was, I AM.". Here Jesus is not only saying that He existed before Abraham but he uses the term "I AM" the very term that can only be used of God.
Here are some more words of Jesus which clearly indicate that He is God.
"I am the living bread which came down from heaven. If anyone eats of this bread, he will live forever; and the bread that I shall give is My flesh, which I shall give for the life of the world." - John 6:51
"I and My Father are one" - John 10:30.
"I am the way, the truth, and the life. No one comes to the Father except through Me." - John 14:6
"If you had known Me, you would have known My Father also; and from now on you know Him and have seen Him." - John 14:7
"... He who has seen Me has seen the Father ..." - John 14:9
There are many other verses that clearly tell us that Jesus is God and can be found throughout the Bible, but none can be clearer when Thomas said to Jesus "My Lord and my God!" - John 20:28
Why did Jesus come to earth?
To understand this, we must realize that we have all fallen short of the standard of God and that all have sinned (Romans 3:23). The consequence of sin is eternal death (Romans 6:23). No one could save us from this terrible consequence except God Himself. But if He were to simply forget our wrongdoings(sin) then it would be a great travesty of justice and would contradict His Holy and Just nature. So, God sent His Son Jesus to die on the cross and by dying He took the penalty of our wrongdoings(sin) on Himself. The demands of God's justice were fully satisfied by Jesus's cruel death on the cross and the demands of God's holiness was fully satisfied by Jesus's perfect life (2 Corinthians 5:21), so it enables Him to forgive and save those who place their faith in Him (Romans 3:26). So, whoever repents of his or her sins and believes that the consequences of his or her sins have been paid on the cross by Lord Jesus will have eternal life instead of eternal death.
He also came to earth and died for us on the cross because He loves us. Bible says But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us. - Romans 5:8 and it also says "He first loved us" - 1 John 4:19. His sacrifice on the cross is the ultimate display of love to save us who did not deserve forgiveness of sins.
Is Jesus alive?
Yes, He was seen alive by over 500 witnesses (1 Corinthians 15:1-11). His resurrection is proof that our sins are forgiven (1 Peter 1:3). He ascended to heaven (Luke 24:51) and is seated on the right hand of the Father (Colossians 3:1). He will return one day (Titus 2:13).
What does knowing Jesus mean?
It is not enough to know certain facts about Jesus. Even Satan and his demons believe in God (James 2:19) and know Jesus (Acts 19:15). On the contrary, knowing Jesus involves believing that He died on the cross personally for you and as a result having a desire to know Him better which is accomplished by reading the Bible. Knowing Him also involves having a personal love relationship with Him through prayer. He desires a relationship with anyone who is willing to open the door (Revelation 3:20). Finally, knowing Him involves living a life that is pleasing to Him which is done by obeying the instructions given in the Bible (2 Peter 1:3).
References:
Uplook Magazine: Is Jesus God?
Fifty reasons why Jesus came to die