People might find it interesting to know that English still has remnants of its case system in its personal pronouns, for example I/me/my/mine, he/him/his, she/her/her, who/whom/whose.

Some people struggle with who/whom but in fact it’s the same as “he” versus “him”: if you replace “who” with “he” in the sentence and it sounds wrong then you should be using “whom”.