This is a poorly constructed sentence, but I think I get the jist of it. Certainly, in studying religion, questions arise. It is the duty of each person to ask questions, seek knowledge, and use logic when trying to understand religion. If you have doubts, they should be temporary, and resolved through the aforementioned search for knowledge and logic. If the doubt persists, at least with regard to whether God exists, you can't possibly consider yourself to be a "believer." How can you follow anything in the Quran, Bible, or Torah if you're not certain of God's existence? Furthermore, what kind of evidence do you want? "Seeing is believing"?
To have doubts is one thing, as long as you seek to resolve those doubts/questions. But to not be sure of a fundamental concept in all religions of the Book, that God does exist, is something alltogether different. Further, you can't be 99% sure that God exists. Either you believe that God exists, you don't believe that God exists, or you're not sure. To say that you're 99% sure that he exists has absolutely no meaning.