Always remember that English is not "phonetic". That means that we do not always say a word the same way that we spell it.
Some words can have the same spelling but different pronunciation, for example:
I like to read [ri:d]. *
I have read [red] that book.*
Some words have different spelling but the same pronunciation, for example:
I have read [red] that book.*
My favourite colour is red [red].*
Learn the 52 Sounds of English
The English language may have 26 letters of the alphabet, but it has double that number of sounds: 52. Knowing and recognizing the 52 sounds will help to give you good pronunciation. Of course, everybody knows that good pronunciation helps our speaking..