What are all those letters we don’t say doing in the word knight? Why is talked the past tense of talk but sang is the past tense of sing? What’s up with m in whom and how come we eat beef but raise cow?

What are all those letters we don’t say doing in the word knight? Why is talked the past tense of talk but sang is the past tense of sing? What’s up with m in whom and how come we eat beef but raise cow?