I would split the question to at least two parts: (1) faith in God and (2) how do we combine what we learn about this universe with our faith in God? The question of philosophy is another box although it is connected to the two questions.
There are many ways how a person starts to believe in God. After the steps towards faith, some get a strong inner convinction that yes, there is God and He listens and shows His love, especially through what Jesus did. For others, the journey starts with more uncertainty and questions, asking are you really there, God?
During the journey, what keeps me believing in God is my experiences of Him. I have learned and experienced enough that I could not anymore deny that there is an unseen reality and someone there (God) acts in ways that fit to what I have been told. What I have experienced fits to the great story of Christianity, much better than to any competing story.
I think that it would be difficult to maintain the faith in God without personal experiences of Him - a theoretical construct would not be a sufficient long-term basis.
As my faith that there is God has become more stable and I have leaned more, I have felt that my certainty of knowing His ways has diminished. As a newborn believer, I suffered from an illusion of knowing much. As that has fallen off, it has forced me to continue the journey more from the position of a disciple or child that is asking and trying to learn.
I believe that God has given to us two ‘books’.
Biblical scriptures contain a special revelation about the will of God - we need to interpret what is told to understand it correctly but the revelation is there.
The other ‘book’ is the book of creation. It is more general but it can reveal about the way how God acts like art can reveal something about the artist.
I also believe that God does not lie. Truth is therefore important for me, more important than what I have earlier believed to be true. If I learn something about our reality, something that holds through all testing, I cannot just deny it. When necessary, I need to adjust my interpretations so that my beliefs are not in conflict with truth. That is a stepwise process where I have to first admit that I do not know everything and then accept that I have to be willing to modify my assumptions where these are in conflict with what is shown to be true.
That includes also having the same attitude towards the teachings of the various religious groups. A church may have a better cumulative understanding of the will of God than an individual but none of the churches has infallible knowledge. For that reason, also the doctrines of the various religious groups need to be tested, compared with what is shown to be true. What is according to truth may be kept, what is in conflict with the facts should be modified or rejected.
This attitude is somewhat demanding in the sense that I cannot just hide behind the backs of religious authorities. Truth challenges at the personal level and sometimes forces to chose. I have chosen to support what the facts tell, even when that puts me outside my former social circles or even outside a denomination.