1. Some examples: I saw her sitting next to him. My brother met her yesterday in the library.
2. "Her hers" doesn't exist in this form, either you use "her" (for example: her bag, her shoes, her umbrella), or "hers" (for example: this umbrella is hers, these shoes are hers, that bag is hers)
3. "He/She" is a subjective pronoun - "he/she" is a subject of the sentence. "Him/Her" is an objective pronoun - "him/her" is an object of the sentence. "His/Hers" is a possessive pronoun - it expresses a possesion :)
I hope it's clear enough, if you have more questions on this, you can either ask here or write me a message :)