I read an article,which talks about the present tense of Greek. The article points out that this aspect means the action is continuing and unending. Further, I found the word "believe", in the present tense in John 3:16. (Also present tense in other verses of New Testament). Now, I am afraid that I may turned unbelieve before. Do I still have hope?
The present tense in Greek has exactly the same force as the English, "he who believes." It is a description of a kind of person, the characterizing feature of said person being their believing in Christ for salvation. As such, it has nothing to do with whether one has spells of doubt or unbelief, or even apostatizes from the way of truth altogether only thereafter to find faith again. That is, it's still true that one who later apostatizes but is reconciled with Christ again in faith to be said to be a "believer in Jesus." He "believes in the Son" over all, as a description of him as a person and his life.
That said, it is a more grevious matter when one apostatizes from the way of truth into unbelief or a life of sin, than one who never new it coming to the throne of mercy for forgiveness for the first time.
2 Peter 2:20-22 (DRB)
[False Christians] promising them liberty, whereas they themselves are the slaves of corruption. For by whom a man is overcome, of the same also he is the slave. 20 For if, flying from the pollutions of the world, through the knowledge of our Lord and Saviour Jesus Christ, they be again entangled in them and overcome: their latter state is become unto them worse than the former. 21 For it had been better for them not to have known the way of justice, than after they have known it, to turn back from that holy commandment which was delivered to them. 22 For, that of the true proverb has happened to them: The dog is returned to his vomit: and, The sow that was washed, to her wallowing in the mire.
That is, not better that they never knew Christ, which is good in itself, but better for their sake (Cf. Mt 26:24), since their punishment is worse than someone who never knew Christ and so could not betray Him (Cf. Heb 10:28-29). Now this speaks of those who do not then return to God (ultimate apostasy) but for those who do, it is better than they be reconciled to God of course than to remain His enemy.
Be consoled with the words of Jesus, that's is possible no matter how far gone to be reconciled to the merciful Father:
Luke 15:11-32 (DRB)
11 And he said: A certain man had two sons: 12 And the younger of them said to his father: Father, give me the portion of substance that falleth to me. And he divided unto them his substance. 13 And not many days after, the younger son, gathering all together, went abroad into a far country: and there wasted his substance, living riotously. 14 And after he had spent all, there came a mighty famine in that country; and he began to be in want. 15 And he went and cleaved to one of the citizens of that country. And he sent him into his farm to feed swine. 16 And he would fain have filled his belly with the husks the swine did eat; and no man gave unto him. 17 And returning to himself, he said: How many hired servants in my father's house abound with bread, and I here perish with hunger? 18 I will arise, and will go to my father, and say to him: Father, I have sinned against heaven, and before thee: 19 I am not worthy to be called thy son: make me as one of thy hired servants. 20 And rising up he came to his father. And when he was yet a great way off, his father saw him, and was moved with compassion, and running to him fell upon his neck, and kissed him. 21 And the son said to him: Father, I have sinned against heaven, and before thee, I am not now worthy to be called thy son. 22 And the father said to his servants: Bring forth quickly the first robe, and put it on him, and put a ring on his hand, and shoes on his feet: 23 And bring hither the fatted calf, and kill it, and let us eat and make merry: 24 Because this my son was dead, and is come to life again: was lost, and is found. And they began to be merry. 25 Now his elder son was in the field, and when he came and drew nigh to the house, he heard music and dancing: 26 And he called one of the servants, and asked what these things meant. 27 And he said to him: Thy brother is come, and thy father hath killed the fatted calf, because he hath received him safe. 28 And he was angry, and would not go in. His father therefore coming out began to entreat him. 29 And he answering, said to his father: Behold, for so many years do I serve thee, and I have never transgressed thy commandment, and yet thou hast never given me a kid to make merry with my friends: 30 But as soon as this thy son is come, who hath devoured his substance with harlots, thou hast killed for him the fatted calf. 31 But he said to him: Son, thou art always with me, and all I have is thine. 32 But it was fit that we should make merry and be glad, for this thy brother was dead and is come to life again; he was lost, and is found.
Without any doubt you have hope. Here are scriptures to prove it:
*I John 1:9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness
*Ezekiel 18:23 Have I any pleasure at all that the wicked should die? saith the Lord GOD: and not that he should return from his ways, and live?
*I John 2:1 My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:
*Jeremiah 3:1 They say, If a man put away his wife, and she go from him, and become another man's, shall he return unto her again? shall not that land be greatly polluted? but thou hast played the harlot with many lovers; yet return again to me, saith the LORD.
*12 Go and proclaim these words toward the north, and say, Return, thou backsliding Israel, saith the LORD; and I will not cause mine anger to fall upon you: for I am merciful, saith the LORD, and I will not keep anger for ever.
*Jeremiah 3:22 Return, ye backsliding children, and I will heal your backslidings. Behold, we come unto thee; for thou art the LORD our God.
*Isaiah 1:18 Come now, and let us reason together, saith the LORD: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool.
*Isaiah 44:22 I have blotted out, as a thick cloud, thy transgressions, and, as a cloud, thy sins: return unto me; for I have redeemed thee.
*Jeremiah 24:7 And I will give them an heart to know me, that I am the LORD: and they shall be my people, and I will be their God: for they shall return unto me with their whole heart.
Peter denied Him thrice. It is all throughout the Bible of His forgiveness and mercy to those who return to him with their whole heart.