Matthew 22:29 (NKJV)
Jesus answered and said to them, "You are mistaken, not knowing the Scriptures nor the power of God."
Anytime you are wondering what to believe in, go to the Bible. What ever it says, believe it.
Anytime you are concerned because you can't figure out how God could have done something, be it a miracle or whatever, you are expressing doubt in His awesome power.
Once you get these two principles right, you can go as deep as you want to in any subject and you never have to fear because you can take comfort that what you don't understand, God does and is able to do all things.
Mark 10:27 (NKJV)
But Jesus looked at them and said, "With men it is impossible, but not with God; for with God all things are possible."