Written English uses a Latin alphabet of 26 letters. How do you represent 45 sounds with 26 letters? Well, here is the problem that has faced the English language through the ages and it also explains why we have so many unusual spellings. For example, the ‘o’ in GOT, WOMEN, NO, WORD, SON, PORT and POLITE is pronounced differently in each word.
There are 2 ways to overcome this: firstly to learn the rules for which sounds can appear with which spellings, and secondly to learn the IPA (phonetic alphabet) so that your pronunciation follows the sounds rather than the written form. IPA may look confusing to begin with, but it can be learnt very quickly and makes pronunciation progress fast.