Their is a personal pronoun which refers to belonging to or associated with a person or people whereas there is an adverb which refers to in, at, or to that place or position. Example :
It was their dream to purchase a BMW.
I am in Saket. You can come and meet me there.
Who’s is the contraction for who is whereas whose is a possessive form of the pronoun who and which. Example :
I want to know who’s there outside in the dark.
Whose bag is lying on my bed?