To know if God is true or not, all you need to do is to trust in him with all your heart and you will know! Obviously, you'll never know him if you do not believe in him. It may not be obvious to you that the more you open yourself up to him, the more he will reveal himself to you, until you and he become one. Now he becomes more real to you than yourself! Now you know him because you know him, not because you've seen some kind of proof. The only way to know God is to allow him to reveal himself to you, to your heart. This is the God to be experienced personally.