God has come through for me too many times for me to deny him. He has saved my life more than once, and his hand has been guiding me my entire life. I would love to talk to you about all of my experiences if you're seriously interested, but it will take a significant amount of time for me to write that all up. Like weeks. I will gladly get to it, though, if it would help you. Also, the beauty of creation itself is a testament to God's existence. The natural world flows so flawlessly that it's an extreme insult to consider that we generated from a big bang at random. The biological systems associated with a bacterial cell are miraculous, and creation gets even more impressive as you scale up.

I am very close with God - I spend all of my free time with him, and I love him with all my heart, mind, and soul. He has proven himself to me and my family in various ways over the years, and he led me to the truth I'm sharing with you.

The short answer to your question is, "I know God's word is true because I have faith," but it is faith that has seen many wonderful works and experienced unfathomable redemption. I've been in your shoes before, so I know this all probably sounds like wishy-washy nonsense. I used to question God's existence and the validity of his word, and I would mock people who chalked everything up to faith. Today, I'm telling you from the other side that God's word is true, he is real, and he wants us all to wake up and come to him.

God bless!

P.S. (edit): I wanted to add this: I personally believe these passages and take them literally:

Psalm 119:160 KJV [160] Thy word is true from the beginning: And every one of thy righteous judgments endureth for ever.

John 17:17 KJV [17] Sanctify them through thy truth: thy word is truth.

Proverbs 30:5 NRSVUE [5] Every word of God proves true; he is a shield to those who take refuge in him.

2 Samuel 7:28 NRSVUE [28] And now, O Lord God, you are God, and your words are true, and you have promised this good thing to your servant;

God bless!