One of the aspects of English as a language is the totally irregular and exception-ridden relationship between how words are written and how they are pronounced.
Worse still, many pronunciations are context-dependent, which puzzles and infuriates everybody – both English speakers and people learning English as a second or subsequent language.
The divergences have a lot to do with the haphazard way in which Middle English evolved as a language and then on to Modern English between 1400 and 1700. The major event in English pronunciation changes, the Great Vowel Shift, occurred during the early days of the printing press, but the major part of the change occurred before the invention of moveable type. So, while the population was busy altering pronunciation, the way the words were written did not change.
Also playing a part is the high percentage of loan words in English from other languages, mainly due to the number of invasions and conquests by other countries.
English is nominally a Germanic language, but the high proportion of loan words, idioms and phrases from other languages makes it a true “mongrel” language.
Here is an attempt to explain (sort of) some of the oddities and rules in English.