Hello XHMIhablante,
Welcome to the forum!
I don't know the rules myself maybe another member can help with that.
That being said, I am strong believer in learning a new language same way a baby learn to speak. You don't give the baby the "rules" on how to pronounce things, you just speak in front of them and eventually their brain recognize the pattern and use it.
If you like to pick bunch of words, we'll be happy to suggest their proper pronunciation to you